Electronic device

ABSTRACT

An electronic device having a novel structure is provided. A battery is provided in each component of an electronic device, whereby the electronic device includes two batteries. The electronic device including the two batteries and a display portion that can be called a flexible display and has a plurality of foldable portions is provided as a novel device.

TECHNICAL FIELD

One embodiment of the present invention relates to an object, a method,or a manufacturing method. The present invention relates to a process, amachine, manufacture, or a composition of matter. One embodiment of thepresent invention relates to a semiconductor device, a display device, alight-emitting device, a power storage device, a lighting device, anelectronic device, or a manufacturing method thereof. One embodiment ofthe present invention relates to an electronic device and an operationsystem thereof.

Note that electronic devices in this specification generally meandevices including secondary batteries, and electro-optical devicesincluding secondary batteries, information terminal devices includingsecondary batteries, and the like are all electronic devices.

BACKGROUND ART

Portable electronic devices and wearable electronic devices are underactive development. For example, a thin portable electronic book isdisclosed in Patent Document 1.

Portable electronic devices and wearable electronic devices save poweras much as possible because they operate using batteries as powersources. Particularly in the case where an electronic device includes acentral processing unit (CPU), processing by the CPU, which consumesmuch power in operation, significantly influences power consumption.

REFERENCE

[Patent Document 1] Japanese Published Patent Application No. S63-15796

DISCLOSURE OF INVENTION

A portable electronic device needs to withstand extended use and thusincorporates high-capacity batteries. In that case, there occurs aproblem that the size and weight of the electronic device are large. Inview of this problem, a small and thin high-capacity battery that can beincorporated in a portable electronic device is under development. Notethat in this specification, “a battery incorporated in an electronicdevice” means a battery that can be freely detached as a battery pack orthe like as well as a battery incorporated so that it cannot be removedto be replaced.

When an electronic device is reduced in size and thickness, a battery islimited by the reduction in the size and thickness. Thus, a circuit, abattery; and the like need to be provided in a smaller space. Thecapacity of the battery, however, is reduced with decrease in thevolume.

Furthermore, a battery generates heat by being charged or discharged andmight thermally influence the surroundings.

An object is how to control power consumption and heat generation whenan electronic device is downsized and a circuit, a battery, and the likeare provided in a smaller space.

An electronic device having a novel structure, specifically, anelectronic device having a novel structure that can change in appearancein various ways is provided.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

A battery is provided in each component of an electronic device, wherebythe electronic device includes a plurality of power sources. Anoperation system that selectively drives only a component to be usedenables power saving in the electronic device including the plurality ofpower sources.

The electronic device further includes a power management circuit(including a power supply monitor circuit) for managing the plurality ofpower sources.

A structure disclosed in this specification is an electronic deviceincluding a central processing unit, a display portion, a touch inputportion, a first receiving portion and a second receiving portion, afirst transmitting portion and a second transmitting portion, and apower management circuit. The central processing unit includes a firstbattery, the first receiving portion, and the first transmittingportion. The first receiving portion has a function of wirelesslycharging the first battery. The display portion includes a secondbattery, the second receiving portion, and the second transmittingportion. The second receiving portion has a function of wirelesslycharging the second battery. The touch input portion is electricallyconnected to the second battery. The power management circuit has afunction of wirelessly transmitting power of one of the first batteryand the second battery to the other so that the battery is charged.

Another structure is an electronic device including a central processingunit, a display portion, a touch input portion, a first receivingportion and a second receiving portion, a first transmitting portion anda second transmitting portion, and a power management circuit. Thecentral processing unit includes a first battery, the first receivingportion, and the first transmitting portion. The first receiving portionhas a function of wirelessly charging the first battery. The displayportion includes a second battery, the second receiving portion, and thesecond transmitting portion. The second receiving portion has a functionof wirelessly charging the second battery. The touch input portionincludes a third battery, a third receiving portion, and a thirdtransmitting portion. The power management circuit has a function ofwirelessly transmitting power of any one of the first battery, thesecond battery; and the third battery to any one of the other batteriesso that the battery is charged.

Note that a circuit is connected to each battery so that the battery canbe wirelessly charged. At least each battery is electrically connectedto the corresponding wireless receiving portion through thecorresponding regulator.

A regulator is a kind of electronic circuit and refers to a circuit thatcontrols output voltage or current such that it is kept constant.Regulators are classified into a linear regulator and a switchingregulator according to the degree of power load. Note that a switchingregulator is also called a DC-DC converter.

The batteries may each be further provided with a transmitting portionthat can transmit power of one battery to any other battery so that thebattery is charged. The power management circuit that manages the amountof power of each battery acquires data on the amount of remaining powerof the battery regularly or constantly and adjusts power as appropriate.

In a device such as a mobile phone or an information terminal (e.g., asmartphone) provided with one power source (battery), all the functionsare stopped when the power source is turned off. When the power sourceis on, a slight amount of power is consumed even if there is afunctional circuit that is not in use because the device is in a standbystate. If there is a functional circuit that is not in use, theelectrical connection between the functional circuit not in use and thebattery may be interrupted to save the power.

As the touch input portion, a capacitive touch sensor can be used, forexample. Examples of capacitive touch sensors include a surfacecapacitive touch sensor and a projected capacitive touch sensor.Examples of projected capacitive touch sensors include a self capacitivetouch sensor and a mutual capacitive touch sensor, which differ mainlyin the driving method. The use of a mutual capacitive type is preferablebecause multiple points can be sensed simultaneously. Note that avariety of sensors (e.g., an optical sensor using a photoelectricconversion element, a pressure sensor using a pressure element) that cansense the approach or the contact of a sensing target such as a fingermay be used. Input operation of the touch input portion in thisspecification is not necessarily performed by touching the displayportion with a finger or the like. The touch input portion in thisspecification includes, in its category, a device for which inputoperation can be performed without contact and by bringing a fingerclose to the display portion.

As the touch input portion, an active touch sensor including a capacitorand a transistor using an oxide semiconductor layer (also referred to asan OS transistor) may be used. In particular, the use of an OStransistor in an active touch sensor enables the potential of a node tobe maintained for a long time, reducing the frequency of refreshoperations.

An operation system that appropriately selects the battery for acomponent to be used among the plurality of batteries in the electronicdevice and determines the battery to be used and reduces powerconsumption of the battery not to be used. Consequently, the length oftime when the information terminal can be used per charge can beincreased.

Furthermore, the power management circuit may perform control such thatpower is supplied to the battery connected to a function that is desiredto be used from any other battery connected to a function that is notused. An operation system that appropriately selects the battery for acomponent to be used from among the plurality of batteries in theelectronic device and adjusts the amount of power in each battery canextend the length of time when the function to be used can be used. Whenthe power management circuit secures any of the batteries as anemergency power supply by the power management circuit, the electronicdevice can be used in emergency. For a mobile phone or the like, forexample, an image is displayed on the display portion when the powersupply is turned on; accordingly, if there is not enough power todisplay an image on the display portion, a phone call cannot be made insome cases. In the case where the electronic device has a plurality ofbatteries one of which is secured as an emergency power supply by thepower management circuit and the emergency power supply is availableonly for a communication function while power supply to the displayportion is stopped, a phone call can be made without displaying an imageon the display portion.

Furthermore, in the case where a single large-sized battery is used foran electronic device having a curved surface or complex shape, theplacement of the battery is limited, and the large-sized battery maydegrade the design. In addition, if small-sized batteries are dottedabout, the risk of explosion and the like can be suppressed; therefore,the safety is higher than the case where a large-sized battery is used.

Specifically, an electronic device including two batteries and a displayportion that can be called a flexible display and has a plurality offoldable portions can be proposed as a novel device. The novel device isan electronic device including a central processing unit, a displayportion, a touch input portion, and a power management circuit. Thedisplay portion is bendable and includes a first region, a secondregion, and a third region. The first region overlaps with the centralprocessing unit. The second region and a first battery partly overlapwith each other in the state where the display portion is unfolded. Thethird region and a second battery partly overlap with each other in thestate where the display portion is unfolded. The first battery has aregion not overlapping with the second battery in the state where thedisplay portion is bent.

This novel device can be small by bending the display portion into an Sshape. The novel device can be thin when the first battery is providedso as not to overlap with the second battery in the state where thedisplay portion is bent (also called the state where the display portionis folded). In that case, the size of the first battery is larger thanthat of the second battery.

In the case where the user carries around and drops an electronic devicehaving only a single large-sized battery, breakage of the battery makesall the functions of the electronic device unavailable. In the casewhere a plurality of small-sized batteries are included, even if one ofthem is broken, some of the functions are still available as long as atleast one of the small-sized batteries can be used. In this manner, inan electronic device including a plurality of small-sized batteries,each of which is used for a different component, some of its functionsare available even if some of its functions are broken. Thus, anelectronic device that hardly becomes out of order can be obtained.

Furthermore, even when one of the small-sized batteries is broken or itsamount of power becomes zero, another battery can be used as asubstitute, owing to the power management circuit, which makes itpossible for the electronic device to be used continuously. Furthermore,even when the amount of power of one of the small-sized batteriesbecomes zero, power can be supplied from a transmitting portionconnected to another battery by wireless charging, owing to the powermanagement circuit. In this manner, the electronic device can be usedfor a long period. In other words, an electronic device including apower management circuit that enables mutual supply of power among aplurality of batteries can be obtained.

A battery is a device that deteriorates as the number of chargesincreases. Owing to the power management circuit adjusting the number ofcharges or selecting batteries to be used, the usage period of batteriescan be extended. In addition, by monitoring the degree of deteriorationof batteries by the power management circuit and appropriately selectingbatteries to be used depending on the degree of deterioration by thepower management circuit, the usage period of the electronic device canbe extended.

It is preferred that at least one of the plurality of small-sizedbatteries provided in the electronic device be a secondary battery thatcan be wirelessly charged.

As the secondary battery, one or more kinds selected from the followingcan be used: a lithium-ion secondary battery such as a lithium polymerbattery, a lithium-ion capacitor, an electric double layer capacitor,and a redox capacitor. The electronic device includes an antenna thatwirelessly receives power and a control means that supplies the receivedpower to a functional circuit.

The antenna included, in the electronic device constitutes acommunication module that realizes a wireless charging function. Thecommunication module may use a charging method corresponding to astandard such as Qi or Powermat. At the time of charge, a plurality ofbatteries may be charged at a time. The antenna included in theelectronic device may constitute a communication module that realizes anear field wireless communication function.

In the case where a plurality of kinds of sensors are included in anelectronic device, since a battery is provided for each component to beused, the user can selectively attach the sensor the user wants to useor detach the sensor. For example, if a control circuit that can controlsensors such as a pulse sensor, a temperature sensor, a positionalinformation sensor (e.g., a GPS), an acceleration sensor, and an angularvelocity sensor, and a connection portion (a connection socket) toconnect the sensor and the control circuit are provided in an electronicdevice, which is used while being worn on the arm, the user can selectthe sensor depending on the function the user wants to use, and thesensor may be connected to the electronic device. In that case, each ofthe sensors has a small-sized battery and a regulator, and the largernumber of functions are used, the larger number of small-sized batteriesare connected. Thus, an electronic device having a plurality ofsmall-sized batteries is obtained.

If a transistor using an oxide semiconductor layer is used for aregulator, reduction in power consumption can be achieved since theoff-state current is small. In particular, a regulator (DC-DC converter)including a control circuit using OS transistors can operate at atemperature of 150° C. or higher. Thus, such a DC-DC converter of anembodiment is preferably used for an electronic device that is likely tooperate at high temperatures.

An oxide semiconductor used for the oxide semiconductor layer to be achannel formation region of the OS transistor preferably contains atleast indium (In) or zinc (Zn). In particular, In and Zn are preferablycontained. A stabilizer for strongly bonding oxygen is preferablycontained in addition to In and Zn. As a stabilizer, at least one ofgallium (Ga), tin (Sn), zirconium (Zr), hafnium (Hf), and aluminum (Al)may be contained.

As another stabilizer, one or more kinds of lanthanoid such as lanthanum(La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu) maybe contained.

As the oxide semiconductor layer used for the OS transistor, forexample, any of the following oxides can be used: indium oxide, tinoxide, zinc oxide, an In—Zn-based oxide, a Sn—Zn-based oxide, anAl—Zn-based oxide, a Zn—Mg-based oxide, a Sn—Mg-based oxide, anIn—Mg-based oxide, an In—Ga-based oxide, an In—Ga—Zn-based oxide (alsoreferred to as IGZO), an In—Al—Zn-based oxide, an In—Sn—Zn-based oxide,a Sn—Ga—Zn-based oxide, an Al—Ga—Zn-based oxide, a Sn—Al—Zn-based oxide,an In—Hf—Zn-based oxide, an In—Zr—Zn-based oxide, an In—Ti—Zn-basedoxide, an In—Sc—Zn-based oxide, an In—Y—Zn-based oxide, anIn—La—Zn-based oxide, an In—Ce—Zn-based oxide, an In—Pr—Zn-based oxide,an In—Nd—Zn-based oxide, an In—Sm—Zn-based oxide, an In—Eu—Zn-basedoxide, an In—Gd—Zn-based oxide, an In—Tb—Zn-based oxide, anIn—Dy—Zn-based oxide, an In—Ho—Zn-based oxide, an In—Er—Zn-based oxide,an In—Tm—Zn-based oxide, an In—Yb—Zn-based oxide, an In—Lu—Zn-basedoxide, an In—Sn—Ga—Zn-based oxide, an In—Hf—Ga—Zn-based oxide, anIn—Al—Ga—Zn-based oxide, an In—Sn—Al—Zn-based oxide, anIn—Sn—Hf—Zn-based oxide, and an In—Hf—Al—Zn-based oxide.

For example, an In—Ga—Zn-based oxide with an atomic ratio ofIn:Ga:Zn=1:1:1, In:Ga:Zn=3:1:2, or In:Ga:Zn=2:1:3, or an oxide with anatomic ratio close to the above atomic ratios can be used.

If an oxide semiconductor film used for a channel formation regioncontains a large amount of hydrogen, the hydrogen and the oxidesemiconductor are bonded to each other, so that part of the hydrogenserves as a donor and causes generation of an electron that is acarrier. As a result, the threshold voltage of the transistor shifts inthe negative direction. It is therefore preferred that after formationof the oxide semiconductor film, dehydration treatment (dehydrogenationtreatment) be performed to remove hydrogen or moisture from the oxidesemiconductor film so that the oxide semiconductor film is highlypurified to contain impurities as little as possible.

Note that oxygen in the oxide semiconductor film is also reduced by thedehydration treatment (dehydrogenation treatment) in some cases.Therefore, it is preferred that oxygen be added to the oxidesemiconductor film to fill oxygen vacancies increased by the dehydrationtreatment (dehydrogenation treatment). In this specification and thelike, supplying oxygen to an oxide semiconductor film may be expressedas oxygen adding treatment, and treatment for making the oxygen contentof an oxide semiconductor film be in excess of that in thestoichiometric composition may be expressed as treatment for making anoxygen-excess state.

In this manner, hydrogen or moisture is removed from the oxidesemiconductor film by the dehydration treatment (dehydrogenationtreatment) and oxygen vacancies therein are filled by the oxygen addingtreatment, whereby the oxide semiconductor film can be turned into ani-type (intrinsic) oxide semiconductor film or a substantially i-type(intrinsic) oxide semiconductor film that is extremely close to ani-type oxide semiconductor film. Note that “substantially intrinsic”means that the oxide semiconductor film contains extremely few (close tozero) carriers derived from a donor and has a carrier density of lowerthan or equal to 1×10¹⁷/cm³, lower than or equal to 1×10¹⁶/cm³, lowerthan or equal to 1×10¹⁵/cm³, lower than or equal to 1×10¹⁴/cm³, or lowerthan or equal to 1×10¹³/cm³.

Thus, the transistor including an i-type or substantially i-type oxidesemiconductor film can have extremely favorable off-state currentcharacteristics. For example, the off-state drain current of thetransistor including the oxide semiconductor film can be 1×10⁻¹⁸ A orless, preferably 1×10⁻²¹ A or less, more preferably 1×10⁻²⁴ A or less atmom temperature (approximately 25° C.), or 1×10⁻¹⁵ A or less, preferably1×10⁻¹⁸ A or less, more preferably 1×10⁻²¹ A or less at 85° C. The offstate of a transistor refers to a state where a gate voltage is muchlower than the threshold voltage in an n-channel transistor.Specifically, the transistor is off when the gate voltage is lower thanthe threshold voltage by 1 V or more, 2 V or more, or 3 V or more.

An oxide semiconductor that is formed may include a non-single crystal,for example. An oxide semiconductor may include CAAC, for example. Notethat an oxide semiconductor including CAAC is referred to as a c-axisaligned crystalline oxide semiconductor (CAAC-OS). The CAAC-OS film isone of oxide semiconductor films having a plurality of c-axis alignedcrystal parts. With a transmission electron microscope (TEM), a combinedanalysis image (also referred to as a high-resolution TEM image) of abright-field image and a diffraction pattern of the CAAC-OS film isobserved. Consequently, a plurality of crystal parts are observedclearly. However, in the high-resolution TEM image, a boundary betweencrystal parts, that is, a grain boundary is not clearly observed. Thus,in the CAAC-OS film, a reduction in electron mobility due to the grainboundary is less likely to occur. According to the high-resolutioncross-sectional TEM image of the CAAC-OS film observed in the directionsubstantially parallel to the sample surface, metal atoms are arrangedin a layered manner in the crystal parts. Each metal atom layer reflectsunevenness of a surface over which the CAAC-OS film is formed(hereinafter, a surface over which the CAAC-OS film is formed isreferred to as a formation surface) or the top surface of the CAAC-OSfilm, and is arranged parallel to the formation surface or the topsurface of the CAAC-OS film. On the other hand, according to the planhigh-resolution TEM image of the CAAC-OS film observed in the directionsubstantially perpendicular to the sample surface, metal atoms arearranged in a triangular or hexagonal arrangement in the crystal parts.However, there is no regularity of arrangement of metal atoms betweendifferent crystal parts. In this specification, the term “parallel”indicates that the angle formed between two straight lines is greaterthan or equal to −10° and less than or equal to 10°, and accordinglyalso includes the case where the angle is greater than or equal to −5°and less than or equal to 5°. In addition, the term “perpendicular”indicates that the angle formed between two straight lines is greaterthan or equal to 80° and less than or equal to 100°, and accordinglyalso includes the case where the angle is greater than or equal to 85°and less than or equal to 95°.

An electronic device with a plurality of power sources, in which abattery is provided for each of components to be used, also has acharacteristic operation system. For example, the operation systemincludes a first battery, a second battery, a third battery, and acontrol portion that manages the first to third batteries, and canwirelessly charge the first to third batteries at a time. Furthermore,the operation system includes at least a plurality of power sources(e.g., secondary batteries) and a control portion such as a CPU, and thecontrol portion manages power of the plurality of power sources. Thenumber of control portion of the electronic device is not limited toone, and may be the same as the number of the plurality of powersources.

Furthermore, an operation system of an electronic device with aplurality of power sources includes a first battery, a second battery, athird battery, and a power management circuit that manages the first tothird batteries, and the first battery wirelessly supplies power to thesecond battery or the third battery. The power management circuitmonitors the amount of power of each battery, and can wirelessly chargeone battery by supplying power from another battery automatically or byoperation of a user as appropriate.

The electronic device is provided with a battery for each of thecomponents to be used, and the operation system selectively drives onlythe component to be used, whereby power consumption can be reduced.Thus, an electronic device having a novel structure can be provided.Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot necessarily have all the effects listed above. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1G illustrate an electronic device of one embodiment of thepresent invention that is unfolded: FIG. 1A is a top view; FIG. 1B is aleft side view; FIG. 1C is a front view; FIG. 1D is a right side view;FIG. 1E is a back view; FIG. 1F is a bottom view; and FIG. 1G is across-sectional view;

FIGS. 2A to 2C are a plan view and cross-sectional views illustratingone embodiment of the present invention;

FIGS. 3A to 3F illustrate an electronic device of one embodiment of thepresent invention;

FIG. 4 is a perspective view illustrating part of the structure of anelectronic device of one embodiment of the present invention;

FIGS. 5A to 5C are a plan view and cross-sectional views illustratingone embodiment of the present invention;

FIG. 6 is a block diagram of an electronic device of one embodiment ofthe present invention;

FIGS. 7A to 7C are a plan view and cross-sectional views illustratingone embodiment of the present invention;

FIGS. 8A to 8D are cross-sectional process views of one embodiment ofthe present invention;

FIGS. 9A to 9D are cross-sectional process views of one embodiment ofthe present invention;

FIGS. 10A to 10D are cross-sectional process views of one embodiment ofthe present invention;

FIGS. 11A1, 11A2, 11B, and 11C are plan views and cross-sectional viewsillustrating embodiments of the present invention;

FIGS. 12A and 12B are cross-sectional views illustrating one embodimentof the present invention;

FIGS. 13A1, 13A2, 13B, and 13C are plan views and cross-sectional viewsillustrating embodiments of the present invention;

FIGS. 14A to 14C are projection views and a perspective viewillustrating the structure of an input/output device of one embodimentof the present invention;

FIGS. 15A to 15C are cross-sectional views illustrating the structure ofan input/output device of one embodiment of the present invention;

FIGS. 16A, 16B1, and 16B2 illustrate the configuration and drivingmethods of a sensing circuit 19 and a converter CONV of one embodimentof the present invention;

FIG. 17A to 17C illustrate the radius of curvature of a surface;

FIGS. 18A to 18D illustrate the center of curvature;

FIGS. 19A to 19F are perspective views, a cross-sectional view, and aschematic view illustrating one embodiment of the present invention;

FIGS. 20A to 20C are a plan view and cross-sectional views illustratingone embodiment of the present invention;

FIG. 21 is a perspective view illustrating an unfolded electronic deviceof one embodiment of the present invention;

FIG. 22 is a perspective view illustrating a folded electronic device ofone embodiment of the present invention;

FIG. 23 is a block diagram of an electronic device of one embodiment ofthe present invention;

FIGS. 24A to 24C are a plan view and cross-sectional views illustratingone embodiment of the present invention;

FIGS. 25A and 25B are a plan view and a cross-sectional viewillustrating one embodiment of the present invention;

FIGS. 26A and 26B are a block diagram and a timing chart of a touchsensor;

FIG. 27 is a circuit diagram of a touch sensor;

FIGS. 28A and 28B are a block diagram and a timing chart of a displaydevice;

FIGS. 29A to 29D illustrate the operations of a display device and atouch sensor;

FIGS. 30A to 30D illustrate the operations of a display device and atouch sensor;

FIG. 31 is a block diagram of a touch panel;

FIGS. 32A and 32B are pixel circuit diagrams; and

FIG. 33 is a timing chart showing the operation of a display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detailwith reference to the drawings. However, the present invention is notlimited to the description below, and it is easily understood by thoseskilled in the art that modes and details disclosed herein can bemodified in various ways. Furthermore, the present invention is notconstrued as being limited to the description of the embodiments.

Embodiment 1

In this embodiment, examples of electronic devices each provided with adisplay portion including a plurality of bendable portions will bedescribed as novel devices that are highly convenient or reliable withreference to FIGS. 1A to 1G, FIGS. 2A to 2C, FIGS. 3A to 3F, FIG. 4,FIGS. 5A to 5C, FIG. 6, FIGS. 17A to 17C, and FIGS. 18A to 18D.Components of the electronic devices will be described below. Note thatthese components cannot be clearly distinguished and one component alsoserves as another component or includes part of another component insome cases.

A user can manually select any of the following two modes for theelectronic device of this embodiment: a mode of folding the device tomake it small by bending the plurality of bendable portions of thedisplay portion; and a mode of unfolding the display portion.

FIGS. 1A to 1G illustrate the unfolded electronic device. FIG. 1A is atop view. FIG. 1B is a left side view. FIG. 1C is a front viewillustrating a surface where the display portion is viewed by a user.FIG. 1D is a right side view. FIG. 1E is a back view. FIG. 1F is abottom view.

A display portion 116 is provided in such a manner that a main screen ispositioned between a first bent region (also referred to as aside-rolled portion 116 a) and a second bent region (also referred to asa side-rolled portion 116 b) as illustrated in FIG. 1C.

The ratio of the length of a short side of a main screen of the displayportion 116 to the length of a long side thereof is 0.9 times or moreand 1.1 times or less the ratio of the length of a short side of adisplay region to the length of a long side thereof. For example, theratio of the length of the short side to the length of the long side isapproximately 9:16.

FIG. 21 is a perspective view illustrating one example of an electronicdevice. The electronic device includes housings 10 to 12 connected witha plurality of hinges 13. Each gap between the housings overlaps with abendable portion of the display portion 116, and the display portion 116can be bent along the portion. FIG. 22 is a perspective viewillustrating the electronic device folded to be small.

As illustrated is FIG. 1E, the display portion overlaps with part ofside surfaces and part of the back surface of the electronic device, andthe overlapping part is a constantly bent display region. The bentregion of the display portion can be bent with a radius of curvature of10 mm or less, preferably 8 mm or less, more preferably 5 mm or less,still more preferably 4 mm or less.

FIGS. 20A to 20C are a modification example of FIGS. 2A to 2C andillustrate three batteries. FIG. 1G is an enlarged cross-sectional viewalong A-A′ in FIG. 1C of the electronic device including threebatteries. As illustrated in FIG. 1G, batteries 112, 117, and 153 areprovided in the respective housings.

The display panel in the above-described structure, which includes thedisplay portion 116, can be changed in form with a radius of curvatureof 1 mm or more, preferably 30 mm or more. A layer including a displayelement is sandwiched between two films. The bent display panel issandwiched between two curves of the two films in cross section.

A description is given of the radius of curvature of a surface withreference to FIGS. 17A to 17C. In FIG. 17A, on a plane 1701 along whicha curved surface 1700 is cut, part of a curve 1702 forming the curvedsurface 1700, is approximate to an arc of a circle, and the radius ofthe circle is referred to as a radius of curvature 1703 and the centerof the circle is referred to as a center of curvature 1704. FIG. 17B isa top view of the curved surface 1700. FIG. 17C is a cross-sectionalview of the curved surface 1700 taken along the plane 1701. When acurved surface is cut along a plane, the radius of curvature of a curve,which is a form of the curved surface, depends on along which plane thecurved surface is cut. When a curved surface is cut by a plane, theradius of curvature of a curve in a cross section differs depending onthe angle between the curved surface and the plane or on the cutposition, and the smallest radius of curvature is defined as the radiusof curvature of a surface in this specification and the like.

In the case of bending a display panel in which a layer 1805 including adisplay element is sandwiched between two films, a radius of curvature1802 of a film 1801 close to a center of curvature 1800 of the displaypanel is smaller than a radius of curvature 1804 of a film 1803 far fromthe center of curvature 1800 (FIG. 18A). When the display panel is bentand has an arc-shaped cross section, compressive stress is applied to asurface of the film on the side closer to the center of curvature 1800and tensile stress is applied to a surface of the film on the sidefarther from the center of curvature 1800 (FIG. 18B).

Note that the cross-sectional shape of the display panel is not limitedto a simple arc shape, and the cross section can be partly arc-shaped;for example, a shape illustrated in FIG. 18C, a wavy shape illustratedin FIG. 18D, or an S shape can be used. When the curved surface of thedisplay panel has a shape with a plurality of centers of curvature, thedisplay panel can change its form such that a curved surface with thesmallest radius of curvature among radii of curvature with respect tothe plurality of centers of curvature, which is a surface of the film onthe side closer to the center of curvature, has a curvature radiusgreater than or equal to 4 mm, preferably greater than or equal to 30mm.

FIG. 2A is a schematic view illustrating the arrangement of thebatteries and the display portion 116 of the back surface, which is nota display surface. A bendable portion 116 e of the display portion thatis indicated by a dotted line in FIG. 2A is located between the battery112 and a system portion 125. A bendable portion 116 d of the displayportion that is indicated by a dotted line in FIG. 2A is located betweenthe batteries 112 and 153. Note that the bendable portions of thedisplay portion are shown by the straight lines in FIG. 2A. Fold linesare not necessarily formed, and the straight line schematicallyindicates a region that can have the smallest radius of curvature 1.

The battery 112 is electrically connected to a regulator 113, and theregulator 113 is electrically connected to the system portion 125including a CPU. The regulator 113 may be connected to a receivingcircuit or a transmitting circuit. FIGS. 2A and 2B illustrate an examplewhere the batteries have substantially the same size; however, oneembodiment of the present invention is not particularly limited to thisexample. For example, the thickness of the battery 112 electricallyconnected to a CPU with large power consumption may be larger than thoseof the other batteries so that the capacity of the battery 112 isincreased.

The battery 153 is electrically connected to the regulator 154. Theregulator 154 is electrically connected to a touch input portion and adisplay portion. The regulator 154 may be connected to a receivingcircuit or a transmitting circuit.

FIG. 2B is a cross-sectional view of the electronic device in FIG. 2Aand illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that isunfolded.

FIG. 2C illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that is bent.The bendable portions 116 d and 116 e of the display portion do notoverlap with the batteries and are bent so that the electronic device issmall.

FIGS. 3A to 3F illustrate the electronic device that is folded to besmall. FIG. 22 is a perspective view of the electronic device. FIG. 3Ais a top view of the electronic device. FIG. 3B is a left side view.FIG. 3C is a front view illustrating a surface where the display portionis viewed by a user. FIG. 3D is a right side view. FIG. 3E is a backview. FIG. 3F is a bottom view.

Also in the case where the electronic device is folded to be small, amain screen is positioned between a first bent region (also referred toas the side-rolled portion 116 a) and the bendable region (also referredto as a side-rolled portion 116 c) as illustrated in FIG. 3C.

The ratio of the length of a short side of the main screen of thedisplay portion 116 to the length of a long side thereof is 0.9 times ormore and 1.1 times or less the ratio of the length of a short side ofthe display region to the length of a long side thereof. For example,the ratio of the length of the short side to the length of the long sideis approximately 9:16.

With such a structure, the second image having approximately the sameratio of the vertical length to the horizontal length as the first imagethat can be displayed so as to fit the first region of the foldeddisplay portion can be displayed so as to fit the display region of theunfolded display portion. Thus, the novel data processing device can behighly convenient or reliable.

FIG. 4 illustrates an example where a touch input portion and a displayportion are electrically connected to one battery 117 with one FPC 4.

The display portion 116 includes two films, and a light-emittingelement, part of a display driver circuit, a touch sensor 152, and partof a sensor driver circuit are provided between the two films. Aseparating layer is provided over a glass substrate, and a transistorand a light-emitting element are formed thereover. After that, the glasssubstrate is removed and a first flexible film 143 is bonded. Inaddition, a separating layer is provided over a glass substrate, and atransistor and the touch sensor 152 are formed thereover. After that,the glass substrate is removed and a second flexible film 144 is bonded.In the structure of FIG. 4, the second flexible film 144 is aligned withand bonded to the first flexible film 143 and the second flexible film144 and the first flexible film 143 function as sealants of thelight-emitting element.

On the circuit board 140, a lead electrode 141 of the battery 117 andthe regulator 118 are electrically connected to each other, and the FPC4 is connected to a connector on the circuit board 140. A layeredlithium-ion secondary battery is used as the battery 117. The FPC 4 hasbranches and three terminals. A first terminal is connected to theconnector on the circuit board 140. A second terminal is connected to aterminal of a touch panel. A third terminal is connected to a terminalof the display portion. Although an example where one FPC is used isdescribed here, two or more FPCs may be used for connection.

Part of a driver circuit 142 is mounted on the FPC 4 and includes partof the sensor driver circuit and part of the driver circuit of thedisplay portion. A circuit partly shared by a touch sensor drivercircuit and the driver circuit of the display portion may be used. Avideo signal or the like to the display portion is supplied from acircuit connected to an end of an FPC 5, or may be supplied by wirelesscommunication using a receiving circuit provided at the end of the FPC5. An input signal of the touch sensor is supplied to the circuitconnected to the end of the FPC 5, or may be supplied to a CPU or thelike by wireless communication using a transmitting circuit provided atthe end of the FPC 5.

One embodiment of the present invention is not limited to the electronicdevice that can be bent along two portions of the display portion as inFIGS. 2A to 2C, and an electronic device of one embodiment of thepresent invention may be bent along three or more portions of thedisplay portion. FIGS. 5A to 5C illustrate an example of an electronicdevice that can be bent along four portions. Further providing bendableportions 116 g and 116 f of the display portion can increase the displayarea of the display portion. FIG. 5B is a cross-sectional view of theelectronic device in FIG. 5A and illustrates the positional relation ofthe system portion 125 including a CPU and each portion of theelectronic device that is unfolded. FIG. 5C illustrates the positionalrelation of the system portion 125 including a CPU and each portion ofthe electronic device that is bent. The bendable portions 116 d, 116 e,116 f, and 116 g of the display portion do not overlap with batteriesand are bent so that the electronic device is small. It can be said thata user can easily hold with both hands the electronic device illustratedin FIGS. 5A to 5C that is unfolded because the batteries are arranged atrespective end portions of the display portion.

FIG. 6 is a block diagram of the device 110. The device 110 in FIG. 6 isan electronic device that includes the two batteries in FIGS. 2A to 2Cand can be small by bending a display portion.

The device 110 of this embodiment includes a control module 115, adisplay module 121, and a power management circuit 127. The controlmodule 115 is a controller that controls the whole device 110,communication, and display of data on the display portion 116.

The control module 115 includes a CPU 111, the battery 112, theregulator 113, a wireless receiving portion 114, and a wirelesstransmitting portion 128.

The display module 121 includes the display portion 116, a displaydriver circuit 119, the battery 117, the regulator 118, the touch sensor152, a sensor driver circuit 159, a field position sensor 150, awireless receiving portion 120, and a wireless transmitting portion 129.

The device 110 can be bent along a plurality of portions of the displayportion 116. Display of an image on a display region hidden by bendingthe device 110 is not performed, whereby power consumption can bereduced. An “image” in this specification includes information that canbe perceived visually, such as characters and symbols. The fold positionsensor 160 can determine the position where the display portion isfolded and supply fold position data. For example, in the case where afold position is determined in advance, a sensor is provided at thatposition. In the case where there are a plurality of positions where thedevice 110 can be bent, a plurality of sensors are arranged in a line ora matrix, so that the coordinates of the bend position can beidentified. For example, the fold position sensor 160 can be providedalong, the periphery of the display region. The fold position sensor 160can be composed of, for example, a switch, a MEMS pressure sensor, apressure sensor, or the like.

Specifically, a mechanical contact switch, a magnetic switch, or thelike may be provided on the display portion to be opened and closed whenthe display portion is unfolded or folded.

Alternatively, a plurality of pressure sensors may be provided on thedisplay portion. Specifically, a film-like piezoelectric element can beattached to the display portion. A rise of pressure with the bendingoperation is sensed with the pressure sensor, whereby the fold positioncan be found.

As the piezoelectric element, for example, an organic piezoelectric filmcan be used. Specifically, a film-like piezoelectric element including apiezoelectric film containing polyamino acid, a piezoelectric filmcontaining polyvinylidene fluoride, a piezoelectric film containingpolyester, a piezoelectric film containing a chiral polymer, or the likecan be used.

Note that the piezoelectric element can serve as both an element for thefold position sensor 160 and an element for a pressure-sensing touchpanel.

The fold position sensor 160 allows one display region to be used as tworegions separated by a folded portion, and an image to be displayed onone of the display regions can be selected. In addition, one or aplurality of images can be selected to be displayed depending on how thedisplay region is folded. To divide one display region into two regionsalong a folded portion, the display region of the display portion 116 ispreferably driven separately by the display driver circuit 119.

Furthermore, the fold position sensor 160 can allow a touch input regionto be used as two regions separated by a folded portion, and one of thetouch input regions can be disabled. The touch input region refers to aregion in which sensing by the touch sensor can be performed and thathas a size substantially the same as that of the display region. To useone touch input region as two regions separated by a folded portion, thetouch input region of the touch sensor 152 is preferably drivenseparately by the sensor driver circuit 159.

The device 110 can be bent along a plurality of portions of the displayportion 116 and does not perform display of an image on the displayregion hidden by bending the device 110, so that power consumption canbe reduced. In addition, the touch sensor of the region where display isnot performed is disabled, so that a malfunction can be prevented.

In this embodiment, a counter substrate (sealing substrate) of thedisplay portion 116 has a touch panel function. Specifically, a displaypanel where a film substrate provided with a transistor using an oxidesemiconductor layer and an organic EL element and a sealing substrateprovided with a touch sensor including a transistor using an oxidesemiconductor layer are bonded to each other is used. In thisembodiment, the sealing substrate is also preferably formed using aflexible material so that part of the display portion can be bent.

As illustrated in an example in FIG. 6, at least part of the sensordriver circuit 159 and at least part of the display driver circuit 119may be included in one IC chip to reduce the number of mountedcomponents.

Each regulator generates and supplies power or a signal needed for eachfunctional circuit from the battery connected to the regulator. Incharging of the battery, the regulator can prevent overcharge or thelike. Note that in FIG. 6, an example where the wireless receivingportion and the wireless transmitting portion are connected to oneregulator is illustrated; however, the wireless receiving portion andthe wireless transmitting portion may be connected to separateregulators.

In the device 110, the power management circuit 127 enables mutualsupply of power between the batteries of the control module 115 and thedisplay module 121. Furthermore, the power management circuit 127 canmonitor the amount of power in the batteries 112 and 117 and execute,automatically or by operation by a user, wireless supply of power fromone of the batteries to the other battery so that the other battery ischarged, as appropriate. Alternatively, the power management circuit 127can monitor the amount of power in the batteries 112 and 117 andexecute, automatically or by operation by a user, wireless supply ofpower from one of a plurality of batteries to one of the other batteriesso that the battery is charged, as appropriate.

In addition, in the device 110, the modules can be individually turnedon or off. An operation system that selectively drives only the moduleto be used allows power saving of the device 110.

After the display module 121 and the control module 115 are turned on todisplay a still image on the display portion 116, the still image cankeep being displayed while only the display module 121 is on even in thecase where the control module 115 is turned off while the still image isdisplayed. Note that in the case where a transistor of the displayportion 116 includes an oxide semiconductor layer, which allows a lowoff-state current (e.g., an oxide material containing In, Ga, and Zn),or in the case where a memory is included in each pixel, a still imagecan keep being displayed for a certain period of time even when powersupply from the battery 117 is stopped after the still image isdisplayed.

Although an example where the display module 121 and the control module115 each include the wireless transmitting portion and the wirelessreceiving portion is described in this embodiment, one embodiment of thepresent invention is not particularly limited to this example. Thebatteries of the display module 121 and the control module 115 may beconnected in series or in parallel. In that case, the electronic deviceincludes at least a receiving circuit for charging the battery withoutcontact (including an antenna for wireless charging) that iselectrically connected to any one of the batteries through theregulator.

FIG. 23 is a block diagram of the device 110 that is partly differentfrom that in FIG. 6. The device 110 in FIG. 23 is an electronic devicethat includes at least the three batteries illustrated in FIGS. 20A to20C and can be made small by bending a display portion.

The device 110 of this embodiment includes the control module 115, thedisplay module 121, the touch input portion 156, and the powermanagement circuit 127. The control module 115 is a controller thatcontrols the whole device 110, communication, and display of data on thedisplay portion 116.

The control module 115 includes the CPU 111, the battery 112, theregulator 113, the wireless receiving portion 114, and the wirelesstransmitting portion 128.

The display module 121 includes the display portion 116, the displaydriver circuit 119, the battery 117, the regulator 118, the wirelessreceiving portion 120, and the wireless transmitting portion 129.

The touch input portion 156 includes the touch sensor 152, the battery153, the regulator 154, the wireless receiving portion 155, and thewireless transmitting portion 150.

In this embodiment, a counter substrate (sealing substrate) of thedisplay portion 116 has a touch panel function. Specifically, a displaypanel where a film substrate provided with a transistor using an oxidesemiconductor layer and an organic EL element and a sealing substrateprovided with a touch sensor including a transistor using an oxidesemiconductor layer are bonded to each other is used. In thisembodiment, the sealing substrate is also preferably formed using aflexible material so that part of the display portion can be bent. Inthis embodiment, an FPC that supplies power to the organic EL elementand an FPC that supplies power to the touch sensor are separatelyprovided and connected to different batteries.

A photosensor may be provided in each pixel of the display panel 116 tomake an optical touch panel. As the touch input portion 156, a resistivetouch panel or a capacitive touch panel may be positioned so as tooverlap with the display portion 116.

Each regulator generates and supplies power or a signal needed for eachfunctional circuit from the battery connected to the regulator. Incharging the battery, the regulator can prevent overcharge or the like.Note that in FIG. 23, an example where the wireless receiving portionand the wireless transmitting portion are connected to one regulator isillustrated; however, the wireless receiving portion and the wirelesstransmitting portion may be connected to separate regulators.

In the device 110, the power management circuit 127 enables mutualsupply of power among the batteries of the control module 115, thedisplay module 121, and the touch input portion 156. Furthermore, thepower management circuit 127 can monitor the amount of power in thebatteries 112, 117, and 153 and execute, automatically or by operationby a user, wireless supply of power from one of the batteries to any ofthe other batteries so that the battery is charged, as appropriate.Alternatively, the power management circuit 127 can monitor the amountof power in the batteries 112, 117, and 153 and execute, automaticallyor by operation by a user, wireless supply of power from one of aplurality of batteries to one of the other batteries so that the batteryis charged, as appropriate.

In addition, in the device 110, the modules can be individually turnedon or off. An operation system that selectively drives only the moduleto be used allows low power consumption of the device 110.

For example, in the case where a user does not use display and desiresto turn oft a display screen without using display, power supply to thedisplay portion 116 is stopped so that the battery 117 is not used, andthe touch input portion 156 and the control module 115 are turned on.When display is desired to be performed on a screen again, the displayscreen can be turned on by touching the screen.

After the display module 121 and the control module 115 are turned on todisplay a still image on the display portion 116, the still image cankeep being displayed while only the display module 12 is on even in thecase where the control module 115 is turned off while the still image isdisplayed. Note that in the case where a transistor of the displayportion 116 includes an oxide semiconductor layer, which allows a lowoff-state current (e.g., an oxide material containing In, Ga, and Zn),or in the case where a memory is included in each pixel, a still imagecan keep being displayed for a certain period of time even when powersupply from the battery 117 is stopped after the still image isdisplayed.

Although an example where the display module 121, the control module115, and the touch input portion 156 include separate batteries isdescribed in this embodiment, the number of batteries is notparticularly limited to three, and the electronic device may include afunctional module and thus four or more batteries, including a batteryof the functional module.

Although an example where the display module 121, the control module115, and the touch input portion 156 each include the wirelesstransmitting portion and the wireless receiving portion is described inthis embodiment, one embodiment of the present invention is notparticularly limited this example. The batteries of the display module121, the control module 115, and the touch input portion 156 may beconnected in series or in parallel. In that case, the electronic deviceincludes at least a receiving circuit for charging the battery withoutcontact (including an antenna for wireless charging) that iselectrically connected to any one of the batteries through theregulator.

Note that the electronic device can be a data terminal device whenprovided with a communication module as a communication function.Furthermore, the electronic device may include a communication modulehaving a near field wireless communication function that allowstelephone calls or the like. In that case, the communication module mayalso include a battery. The electronic device may have any otherfunction and include, for example, a sensor (a sensor having a functionof measuring force, displacement, position, speed, acceleration, angularvelocity, rotational speed, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), a microphone, or the like.

The electronic device may further be provided with a slot for insertionof a SIM card, a connector portion for connecting a USB device such as aUSB memory.

As described above, the electronic device includes a plurality ofbatteries that are provided in corresponding units (modules orfunctions) in the electronic device and managed by the power managementcircuit 127. In the electronic device including the plurality ofbatteries, an operation system that selectively drives only the moduleto be used allows power saving. The power management circuit 127 canmonitor the amount of power in the batteries and execute, automaticallyor by operation by a user, wireless supply of power from one of thebatteries to any of the other batteries so that the battery is charged,as appropriate. An operation system that appropriately selects thebattery for a component to be used from the plurality of batteries inthe electronic device and adjusts the amount of power in each batterycan extend time when the function to be used can be used.

The batteries each include a communication module having a non-contactcharging function and can be controlled to be charged at the same time.In addition, the batteries each include a transmitting and receivingportion and can adjust the amount of power with the power managementcircuit; thus, power can be mutually supplied among the batteries.

Embodiment 2

In this embodiment, an example that is partly different from Embodiment1 will be described with reference to FIGS. 7A to 7C. Note that the samereference numerals are used for the same portions as those in FIGS. 2Ato 2C, and description of the portions with the same reference numeralsis omitted here.

An example where two batteries with substantially the same size are usedis described in Embodiment 1, whereas FIG. 7A illustrates an examplewhere batteries have a different size and arrangement from the batteriesin Embodiment 1. A display region of the display portion 116 has a sizeof approximately 5.9 inches.

FIG. 7A is a schematic view illustrating the arrangement of thebatteries and the display portion 116 of the back surface, which is nota display surface. The bendable portion 116 d of the display portionindicated by a dotted line in FIG. 7A is located between the battery 112and a battery 753.

The battery 112 is electrically connected to the regulator 113, and theregulator 113 is electrically connected to the system portion 125including a CPU. The regulator 113 may be connected to a receivingcircuit or a transmitting circuit.

The battery 753 is electrically connected to a regulator 754. Theregulator 754 is electrically connected to a touch input portion and adriver circuit of the display portion 116. The regulator 754 may beconnected to a receiving circuit or a transmitting circuit.

FIG. 7B is a cross-sectional view of the electronic device in FIG. 7Aand illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that isunfolded.

FIG. 7C illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that is bent.The battery 112 is positioned so as not to overlap with the batter 753when the electronic device is bent. By thus being made small, theelectronic device can have a smaller thickness than the electronicdevice of Embodiment 1 that is made small. The bendable portions 116 dand 116 e of the display portion do not overlap with the batteries andare bent so that the electronic device is small.

In the case where three batteries are provided in the electronic device,the sizes thereof are not necessarily substantially the same. FIG. 24Aillustrates an example where two batteries have a different size andarrangement. A display region of the display portion 116 has a size ofapproximately 5.9 inches.

FIG. 24A is a schematic view illustrating the arrangement of thebatteries and the display portion 116 of the back surface, which is nota display surface. The bendable portion 116 e of the display portionindicated by a dotted line in FIG. 24A is located between the battery112 and a battery 717. The bendable portion 116 d of the display portionindicated by a dotted line in FIG. 24A is located between the batteries717 and 753.

The battery 112 is electrically connected to the regulator 113, and theregulator 113 is electrically connected to the system portion 125including a CPU. The regulator 113 may be connected to a receivingcircuit or a transmitting circuit.

The battery 717 is electrically connected to a regulator 718. Theregulator 718 is electrically connected to a driver circuit of thedisplay portion 116. The regulator 718 may be connected to a receivingcircuit or a transmitting circuit.

The battery 753 is electrically connected to a regulator 754. Theregulator 754 is electrically connected to a touch input portion. Theregulator 754 may be connected to a receiving circuit or a transmittingcircuit.

FIG. 24B is a cross-sectional view of the electronic device in FIG. 24Aand illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that isunfolded.

FIG. 24C illustrates the positional relation of the system portion 125including a CPU and each portion of the electronic device that is bent.When the electronic device is bent, the battery 112 overlaps with thebatteries 717 and 753 but the battery 717 does not overlap with thebattery 753. By thus being made small, the electronic device can have asmaller thickness than the electronic device of Embodiment 1 that ismade small. The bendable portions 116 d and 116 e of the display portiondo not overlap with the batteries and are bent so that the electronicdevice is small.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 3

In Embodiment 1, the display portion using the first flexible film 143and the second flexible film 144 is described, whereas in thisembodiment, a flexible display panel is fabricated using a separationmethod. In this embodiment, an example of fabricating the flexibledisplay panel using a separation layer will be described below.

First, a separation layer 203 is formed over a formation substrate 201,and a layer 205 to be separated (hereinafter referred to as a layer 205)is formed over the separation layer 203 (FIG. 8A). In addition, aseparation layer 223 is formed over a formation substrate 221, and alayer 225 to be separated (hereinafter referred to as a layer 225) isformed over the separation layer 223 (FIG. 8B).

For example, when a tungsten film is used as the separation layer, atungsten oxide film can be formed between a layer to be separated andthe tungsten film by N₂O plasma treatment. Forming the tungsten oxidefilm by N₂O plasma treatment enables separation of the layer to beseparated with a weak force. When the separation is caused at theinterface between the tungsten film and the tungsten oxide film, thetungsten oxide film is left on the side of the layer to be separated insome cases. The left tungsten oxide film might adversely affect theproperties of a transistor. Thus, a step of removing the left tungstenoxide film is preferably performed after the step of separating theseparation layer and the layer to be separated.

In one embodiment of the present invention, a tungsten film with athickness of greater than or equal to 0.1 nm and less than 200 nm isformed over the substrate.

Next, the formation substrate 201 and the formation substrate 221 areattached to each other by using a bonding layer 207 and a frame-likebonding layer 211 so that the surfaces over which the layers to beseparated are formed face each other, and then, the bonding layer 207and the frame-like bonding layer 211 are cured (FIG. 8C). Here, theframe-like bonding layer 211 and the bonding layer 207 in a regionsurrounded by the frame-like bonding layer 211 are provided over thelayer 225 and after that, the formation substrate 201 and the formationsubstrate 221 face each other and are attached to each other.

Note that the formation substrate 201 and the formation substrate 221are preferably attached to each other in a reduced-pressure atmosphere.

Note that although FIG. 8C illustrates the case where the separationlayer 203 and the separation layer 223 are different in size, separationlayers having the same size as illustrated in FIG. 8D may be used.

The bonding layer 207 is provided to overlap with the separation layer203, the layer 205, the layer 225, and the separation layer 223. Then,edges of the bonding layer 207 are preferably positioned inside an areabetween at least edges of either the separation layer 203 or theseparation layer 223 (the separation layer which is desirably separatedfirst). Accordingly, strong adhesion between the formation substrate 201and the formation substrate 221 can be suppressed thus, a decrease inyield of a subsequent separating process can be suppressed.

Next, a separation trigger is formed by laser irradiation (FIGS. 9A and9B).

Either the formation substrate 201 or the formation substrate 221 may beseparated first. In the case where the separation layers differ in size,a substrate over which a larger separation layer is formed may beseparated first or a substrate over which a smaller separation layer isformed may be separated first. In the case where an element such as asemiconductor element, a light-emitting element, or a display element isformed only over one of the substrates, the substrate on the side wherethe element is formed may be separated first or the other substrate maybe separated first. Here, the formation substrate 201 is separatedfirst.

A region where the bonding layer 207 in a cured state or the frame-likebonding layer 211 in a cured state, the layer 205, and the separationlayer 203 overlap with one another is irradiated with laser light. Here,the bonding layer 207 is in a cured state and the frame-like bondinglayer 211 is not in a cured state, and the bonding layer 207 in a curedstate is irradiated with laser light (see an arrow P3 in FIG. 9A).

Part of the layer 205 is removed; thus, the separation trigger can beformed (see a region surrounded by a dashed line in FIG. 9B). At thistime, not only a part of the layer 205 but also the separation layer 203or the bonding layer 207 may be partly removed.

It is preferred that laser light irradiation be performed from the sideof the substrate provided with the separation layer that is desirablyseparated. In the case where a region where the separation layer 203 andthe separation layer 223 overlap with each other is irradiated withlaser light, the formation substrate 201 and the separation layer 203can be selectively separated by cracking only the layer 205 of thelayers 205 and 225 (see a region surrounded by a dotted line in FIG.9B).

When a separation trigger is formed in both the layer 205 on theseparation layer 203 side and the layer 225 on the separation layer 223side in the case where the region where the separation layer 203 and theseparation layer 223 overlap with each other is irradiated with laserlight, it might be difficult to selectively separate one of theformation substrates. Therefore, laser light irradiation conditions arerestricted so that only one of the layers to be separated is cracked, insome cases.

Then, the layer 205 and the formation substrate 201 are separated fromeach other from the formed separation trigger (FIGS. 9C and 9D).Consequently, the layer 205 can be transferred from the formationsubstrate 201 to the formation substrate 221.

The layer 205 that is separated from the formation substrate 201 in thestep in FIG. 9D is attached to a substrate 231 with a bonding layer 233,and the bonding layer 233 is cured (FIG. 10A).

Next, a separation trigger is formed by a sharp knife such as a cutter(FIGS. 10B and 10C).

In the case where the substrate 231 on the side where the separationlayer 223 is not provided can be cut by a knife or the like, a cut maybe made in the substrate 231, the bonding layer 233, and the layer 225(see arrows P5 in FIG. 10B). Consequently, part of the layer 225 can beremoved; thus, the separation trigger can be formed (see a regionsurrounded by a dashed line in FIG. 10C).

For example, in the case where there is a region in which the formationsubstrate 221 and the substrate 231 are attached to each other using thebonding layer 233 without overlapping with the separation layer 223,there is a portion in which the separation is not performed in asubsequent separating process depending on a degree of adhesion betweenthe formation substrate 221 and the substrate 231, so that yield of thesubsequent separating process might be decreased. Therefore, a cut ispreferably made in a frame shape in a region where the bonding layer 233in a cured state and the separation layer 223 overlap with each other toform a separation trigger in a form of a solid line. This can improvethe yield of the separating process.

Then, the layer 225 and the formation substrate 221 are separated fromeach other from the formed separation trigger (FIG. 10D), so that thelayer 225 can be transferred from the formation substrate 221 to thesubstrate 231.

The formation substrate 221 and the layer 225 may be separated from eachother by filling the interface between the separation layer 223 and thelayer 225 with a liquid such as water. A portion between the separationlayer 223 and the layer 225 absorbs a liquid through a capillarityaction, facilitating separation. Furthermore, an adverse effect on thefunctional element included in the layer 225 due to static electricitycaused at separation (e.g., a phenomenon in which a semiconductorelement is damaged by static electricity) can be suppressed. Note that aliquid may be sprayed in an atomized form or in a vaporized form.Examples of liquid include pure water, an organic solvent, a neutralsolution, an alkali solution, an acid solution, and an aqueous solutionin which a salt is dissolved.

In the separating method of one embodiment of the present inventiondescribed above, separation is performed in such a manner that aseparation trigger is formed by a sham knife or the like and then theinterface between the separation layer and the layer to be separated ismade in a separable state. This can improve the yield of the separatingprocess.

In addition, bonding of a substrate included in a device that is desiredto be fabricated can be performed after the following procedure: a pairof formation substrates each provided with a layer to be separated areattached to each other and then separation is performed. Therefore,formation substrates having low flexibility can be attached to eachother when the layers to be separated are attached to each other,whereby alignment accuracy at the time of attachment can be improvedcompared to the case where flexible substrates are attached to eachother.

An example of a flexible light-emitting device that can be fabricatedusing the separating method described above will be described below.

FIGS. 11A1 to 11C, FIGS. 12A and 12B, and FIGS. 13A1 to 13C illustrateexamples of flexible light-emitting devices each including an organic ELelement as a light-emitting element. The flexible light-emitting deviceof this embodiment can be bent in any direction with, for example, aradius of curvature of 1 mm to 150 mm inclusive. The number of bendportions may be one or more than one; for example, the light-emittingdevice can be bent in two or three.

For example, a light-emitting device of one embodiment of the presentinvention includes a first flexible substrate, a second flexiblesubstrate, a light-emitting element between the first flexible substrateand the second flexible substrate, a first insulating layer between thefirst flexible substrate and the light-emitting element, and a firstbonding layer between the second flexible substrate and thelight-emitting element. The light-emitting element includes a layercontaining a light-emitting organic compound between a pair ofelectrodes. The water vapor permeability of the first insulating layeris less than 1×10⁻⁵ g/m²·day.

The light-emitting device preferably further includes a secondinsulating layer between the second flexible substrate and the firstbonding layer. The water vapor permeability of the second insulatinglayer is preferably less than 1×10⁻⁵ g/m²·day. The light-emitting devicepreferably further includes a second bonding layer that surrounds thefirst bonding layer like a frame.

Note that the light-emitting device in this specification includes, inits category, a display device using a light-emitting element. Thecategory of the light-emitting device includes a module in which alight-emitting element is provided with a connector such as ananisotropic conductive film or a tape carrier package (TCP); a module inwhich a printed wiring board is provided at the end of a TCP; and amodule in which an integrated circuit (IC) is directly mounted on alight-emitting element by a chip on glass (COG) method. Moreover,lighting equipment and the like may be included in the category of thelight-emitting device.

Structural Example 1

FIG. 11A1 is a plan view of a light-emitting device, and FIG. 11B is across-sectional view along dashed-dotted line X3-Y3 in FIG. 11A1. Thelight-emitting device illustrated in FIG. 11B is a top-emissionlight-emitting device fabricated using a side-by-side method. In thisembodiment, the light-emitting device can express one color withlight-emitting units of three colors of red (R), green (G), and blue (B)or with light-emitting units of four colors of red (R), green (G), blue(B), and white (W), for example; however, colors other than R, G, and B,such as yellow, cyan, and magenta, may be used as color elements.

The light-emitting device illustrated in FIG. 11A1 includes alight-emitting portion 491, a driver circuit portion 493, and a flexibleprinted circuit (FPC) 495. An organic EL element and a transistorincluded in the light-emitting portion 491 and the driver circuitportion 493 are sealed by a flexible substrate 420, a flexible substrate428, a frame-like bonding layer 404, and a bonding layer 407. FIG. 11Billustrates an example where the conductive layer 457 and the connector497 are connected to each other through an opening portion of theframe-like bonding layer 404.

The light-emitting device illustrated in FIG. 11B includes the flexiblesubstrate 420, a bonding layer 422, an insulating layer 424, atransistor 455, an insulating layer 463, an insulating layer 465, aninsulating layer 405, an organic EL element 450 (a first electrode 401,an EL layer 402, and a second electrode 403), the frame-like bondinglayer 404, the bonding layer 407, the flexible substrate 428, and theconductive layer 457. The flexible substrate 428, the bonding layer 407,and the second electrode 403 transmit visible light.

In the light-emitting portion 491 of the light-emitting device in FIG.11B, the transistor 455 and the organic EL element 450 are provided overthe flexible substrate 420 with the bonding layer 422 and the insulatinglayer 424 provided therebetween. The organic EL element 450 includes thefirst electrode 401 over the insulating layer 465, the EL layer 402 overthe first electrode 401, and the second electrode 403 over the EL layer402. The first electrode 401 is electrically connected to a sourceelectrode or a drain electrode of the transistor 455. The firstelectrode 401 preferably reflects visible light. The end portion of thefirst electrode 401 is covered with the insulating layer 405.

The driver circuit portion 493 includes a plurality of transistors. FIG.11B illustrates one of the transistors in the driver circuit portion493.

The conductive layer 457 is electrically connected to an external inputterminal through which a signal (e.g., a video signal, a clock signal, astart signal, and a reset signal) or a potential from the outside istransmitted to the driver circuit portion 493. Here, the FPC 495 isprovided as the external input terminal.

To prevent an increase in the number of fabricating steps, theconductive layer 457 is preferably formed using the same material andthe same step(s) as those of the electrode or the wiring in thelight-emitting portion or the driver circuit portion. Here, the exampleis described in which the conductive layer 457 is formed using the samematerial and the same step(s) as those of the electrodes of thetransistor.

The insulating layer 463 has an effect of inhibiting diffusion ofimpurities into a semiconductor included in the transistor. As theinsulating layer 465, an insulating layer having a planarizationfunction is preferably selected in order to reduce surface unevennessdue to the transistor.

The frame-shaped bonding layer 404 preferably has a more excellent gasbarrier property than the bonding layer 407, in which case moisture andoxygen from the outside can be prevented from entering thelight-emitting device. Thus, the light-emitting device can be highlyreliable.

In Structural Example 1, light emission of the organic EL element 450 isextracted from the light-emitting device through the bonding layer 407.For this reason, the bonding layer 407 preferably has a more excellentlight-transmitting property than the frame-like bonding layer 404.Furthermore, the bonding layer 407 preferably has a higher refractiveindex than the frame-like bonding layer 404. In addition, it ispreferred that the volume of the bonding layer 407 be less reduced bycuring than that of the frame-like bonding layer 404.

The light-emitting device described in Structural Example 1 can befabricated with high yield using the separating method described above.According to the separating method, the insulating layer 424 and thetransistors are formed over the formation substrate, as the layer to beseparated, whereby the insulating layer 424 and the transistors can beformed at high temperature. The use of the insulating layer 424 and thetransistors formed at high temperature enables the light-emitting deviceto have high reliability. Note that the organic EL element 450 or thelike may also be formed as the layer to be separated.

Structural Example 2

FIG. 11A2 is a plan view of the light-emitting device, and FIG. 11C is across-sectional view along dashed-dotted line X4-Y4 in FIG. 11A2. Thelight-emitting device illustrated in FIG. 11C is a bottom-emissionlight-emitting device using a color filter method.

The light-emitting device illustrated in FIG. 11C includes the flexiblesubstrate 420, the bonding layer 422, the insulating layer 424, atransistor 454, the transistor 455, the insulating layer 463, thecoloring layer 432, the insulating layer 465, a conductive layer 435, aninsulating layer 467, the insulating layer 405, the organic EL element450 (the first electrode 401, the EL layer 402, and the second electrode403), the bonding layer 407, the flexible substrate 428, and theconductive layer 457. The flexible substrate 420, the bonding layer 422,the insulating layer 424, the insulating layer 463, the insulating layer465, the insulating layer 467, and the first electrode 401 transmitvisible light.

In the light-emitting portion 491 of the light-emitting deviceillustrated in FIG. 11C, the switching transistor 454, the currentcontrol transistor 455, and the organic EL element 450 are provided overthe flexible substrate 420 with the bonding layer 422 and the insulatinglayer 424 provided therebetween. The organic EL element 450 includes thefirst electrode 401 over the insulating layer 467, the EL layer 402 overthe first electrode 401, and the second electrode 403 over the EL layer402. The first electrode 401 is electrically connected to the sourceelectrode or the drain electrode of the transistor 455 through theconductive layer 435. The end portion of the first electrode 401 iscovered with the insulating layer 405. It is preferred that the secondelectrode 403 reflect visible light. Moreover, the light-emitting deviceincludes the coloring layer 432 over the insulating layer 463 so as tooverlap with the organic EL element 450.

The driver circuit portion 493 includes a plurality of transistors. FIG.11C illustrates two of the transistors in the driver circuit portion493.

The conductive layer 457 is electrically connected to an external inputterminal through which a signal or a potential from the outside istransmitted to the driver circuit portion 493. Here, the example inwhich the FPC 495 is provided as the external input terminal isdescribed. Moreover, here, the example in which the conductive layer 457is formed using the same material and the same step(s) as those of theconductive layer 435 is described.

The insulating layer 463 has an effect of suppressing diffusion ofimpurities into a semiconductor included in the transistor. As theinsulating layer 465 and the insulating layer 467, an insulating layerhaving a planarization function is preferably selected in order toreduce surface unevenness due to the transistors and the wirings.

Note that a touch sensor may be provided so as to overlap with theflexible substrate 420 as illustrated in FIG. 12A. The touch sensorincludes a conductive layer 441, a conductive layer 442, and aninsulating layer 443. As illustrated in FIG. 12B, a flexible substrate444 may be provided between the flexible substrate 420 and the touchsensor. Note that the touch sensor may be provided between the flexiblesubstrate 420 and the flexible substrate 444. An FPC 445 for the touchsensor may further be provided.

The light-emitting device described in Structural Example 2 can befabricated with high yield using the separating method described above.According to the separating method, the insulating layer 424 and thetransistors are formed over the formation substrate, as the layer to beseparated, whereby the insulating layer 424 and the transistors can beformed at high temperature. The use of the insulating layer 424 and thetransistors formed at high temperature enables the light-emitting deviceto have high reliability. Note that the organic EL element 450 or thelike may also be formed as the layer to be separated.

Structural Example 3

FIG. 13A1 is a plan view of a light-emitting device, and FIG. 13B is across-sectional view along dashed-dotted line X5-Y5 in FIG. 13A1. Thelight-emitting device illustrated in FIG. 13A1 is a top-emissionlight-emitting device using a color filter method.

The light-emitting device illustrated in FIG. 13B includes the flexiblesubstrate 420, the bonding layer 422, the insulating layer 424, thetransistor 455, the insulating layer 463, the insulating layer 465, theinsulating layer 405, a spacer 496, the organic EL element 450 (thefirst electrode 401, the EL layer 402, and the second electrode 403),the bonding layer 407, an overcoat 453, a light-blocking layer 431, thecoloring layer 432, an insulating layer 226, a bonding layer 426, theflexible substrate 426, and the conductive layer 457. The flexiblesubstrate 428, the bonding layer 426, the insulating layer 226, thebonding layer 407, the overcoat 453, and the second electrode 403transmit visible light.

In the light-emitting portion 491 of the light-emitting device in FIG.13B, the transistor 455 and the organic EL element 450 are provided overthe flexible substrate 420 with the bonding layer 422 and the insulatinglayer 424 provided therebetween. The organic EL element 450 includes thefirst electrode 401 over the insulating layer 465, the EL layer 402 overthe first electrode 401, and the second electrode 403 over the EL layer402. The first electrode 401 is electrically connected to a sourceelectrode or a drain electrode of the transistor 455. The end portion ofthe first electrode 401 is covered with the insulating layer 405. Thefirst electrode 401 preferably reflects visible light. The spacer 496 isprovided over the insulating layer 405. The spacer 496 allows adjustmentof the distance between the flexible substrate 420 and the flexiblesubstrate 428.

Moreover, the light-emitting device includes the coloring layer 432overlapping with the organic EL element 450 with the bonding layer 407provided therebetween, and the light-blocking layer 431 overlapping withthe insulating layer 405 with the bonding layer 407 providedtherebetween.

The driver circuit portion 493 includes a plurality of transistors. FIG.13B illustrates one of the transistors in the driver circuit portion493.

The conductive layer 457 is electrically connected to an external inputterminal through which a signal or a potential from the outside istransmitted to the driver circuit portion 493. Here, the example inwhich the FPC 495 is provided as the external input terminal isdescribed. Moreover, here, the example in which the conductive layer 457is formed using the same material and the same step(s) as those of theelectrodes of the transistor 455 is described.

In the light-emitting device illustrated in FIG. 13B, the connector 497is located over the insulating layer 226. The connector 497 is connectedto the conductive layer 457 through an opening formed in the flexiblesubstrate 428, the bonding layer 426, the insulating layer 226, thebonding layer 407, the insulating layer 465, and the insulating layer463. Moreover, the connector 497 is connected to the FPC 495. The FPC495 and the conductive layer 457 are electrically connected to eachother through the connector 497. In the case where the conductive layer457 and the flexible substrate 428 overlap with each other, theconductive layer 457, the connector 497, and the FPC 495 areelectrically connected to one another by forming an opening in theflexible substrate 428 (or using a flexible substrate having anopening).

The insulating layer 424 preferably has an excellent gas barrierproperty, in which case moisture and oxygen from the flexible substrate420 side can be prevented from entering the light-emitting device.Similarly, the insulating layer 226 preferably has an excellent gasbarrier property, in which case moisture and oxygen from the flexiblesubstrate 428 side can be prevented from entering the light-emittingdevice.

The light-emitting device described in Structural Example 3 can befabricated with high yield using the separating method described above.According to the separating method, the insulating layer 424, thetransistors, the organic EL element 450, and the like are formed overthe formation substrate, as a layer to be separated. Then, theinsulating layer 226, the coloring layer 432, the light-blocking layer431, and the like, are formed over another formation substrate, as alayer to be separated. After the two formation substrates are bonded toeach other, the layers to be separated and the formation substrates areseparated from each other. Then, the layers to be separated and theflexible substrates are bonded to each other with a bonding layer, sothat the light-emitting device described in Structural Example 3 can befabricated.

According to the separating method of one embodiment of the presentinvention, an insulating layer and transistors can be formed over aformation substrate at high temperature. The use of the insulating layer424, the insulating layer 226, and the transistors formed at hightemperature enables the light-emitting device to have high reliability.The insulating layers with an excellent gas barrier property (insulatinglayers 226 and 424) formed at high temperature can be provided over andbelow the organic EL element 450. This can prevent impurities such asmoisture from entering the organic EL element 450.

Structural Example 4

FIG. 13A2 is a plan view of a light-emitting device, and FIG. 13C is across-sectional view along dashed-dotted line X6-Y6 in FIG. 13A2. Thelight-emitting device illustrated in FIG. 13A2 is a top-emissionlight-emitting device using a color filter method.

The light-emitting device illustrated in FIG. 13C includes the flexiblesubstrate 420, the bonding layer 422, the insulating layer 424, thetransistor 455, the insulating layer 463, the insulating layer 465, theinsulating layer 405, the organic EL element 450 (the first electrode401, the EL layer 402, and the second electrode 403), a frame-likebonding layer 404 a, a frame-like bonding layer 404 b, the bonding layer407, the overcoat 453, the fight-blocking layer 431, the coloring layer432, the insulating layer 226, the bonding layer 426, the flexiblesubstrate 428, and the conductive layer 457. The flexible substrate 428,the bonding layer 426, the insulating layer 226, the bonding layer 407,the overcoat 453, and the second electrode 403 transmit visible light.

In the light-emitting portion 491 of the light-emitting device in FIG.13C, the transistor 455 and the organic EL element 450 are provided overthe flexible substrate 420 with the bonding layer 422 and the insulatinglayer 424 provided therebetween. The organic EL element 450 includes thefirst electrode 401 over the insulating layer 465, the EL layer 402 overthe first electrode 401, and the second electrode 403 over the EL layer402. The first electrode 401 is electrically connected to a sourceelectrode or a drain electrode of the transistor 455. The end portion ofthe first electrode 401 is covered with the insulating layer 405. Thefirst electrode 401 preferably reflects visible light. Moreover, thelight-emitting device includes the coloring layer 432 overlapping withthe organic EL element 450 with the bonding layer 407 providedtherebetween, and the light-blocking layer 431 overlapping with theinsulating layer 405 with the first bonding layer 407 providedtherebetween.

The driver circuit portion 493 includes a plurality of transistors. FIG.13C illustrates one of the transistors in the driver circuit portion493. An example where the driver circuit portion 493 is positioned in aregion surrounded by the frame-like bonding layers 404 a and 404 b isdescribed in this embodiment; however, the driver circuit portion 493may be positioned outside one or both of the frame-like bonding layers404 a and 404 b.

The conductive layer 457 is electrically connected to an external inputterminal through which a signal or a potential from the outside istransmitted to the driver circuit portion 493. Here, the example inwhich the FPC 495 is provided as the external input terminal isdescribed. Moreover, here, an example in which the conductive layer 457is formed using the same material and the same step(s) as those of theelectrodes of the transistor 455 is described. The connector 497 overthe insulating layer 226 is connected to the conductive layer 457.Moreover, the connector 497 is connected to the FPC 495. The FPC 495 andthe conductive layer 457 are electrically connected to each otherthrough the connector 497.

The conductive layer 457 is preferably positioned outside the frame-likebonding layer 404 a because the entry of impurities such as moistureinto the organic EL element 450 can be prevented even in the case wheremoisture and the like easily enter from a connection portion between theFPC 495 and the connector 497 and a connection portion between theconnector 497 and the conductive layer 457.

The light-emitting device illustrated in FIG. 13C is different from thatin FIG. 13B in that the insulating layer 465 is covered at a sidesurface of the light-emitting device. In the case of using an organicinsulating material or the like having an inferior gas barrier propertyas a material of the insulating layer 465, the insulating layer 465 ispreferably covered at the side surface of the light-emitting device. Inaddition, the frame-like bonding layer having an excellent gas barrierproperty is preferably positioned at the side surface of thelight-emitting device to increase the reliability of the light-emittingdevice. Note that the insulating layer 465 is not necessarily covered atan end portion of the light-emitting device depending on a material orthe like for the insulating layer 465, as illustrated in FIG. 13B.

The frame-shaped bonding layer 404 a and the frame-shaped bonding layer404 b each preferably have a more excellent gas barrier property thanthe bonding layer 407, in which case moisture and oxygen from the sidesurface of the light-emitting device can be prevented from entering thelight-emitting device. Thus, the light-emitting device can be highlyreliable.

For example, the frame-like bonding layer 404 a has the lowest watervapor permeability among the bonding layer 407, the frame-like bondinglayer 404 a, and the frame-like bonding layer 404 b. Particularly whenthe frame-like bonding layer 404 b includes a desiccating agent or thelike that adsorbs moisture, entry of moisture is suppressed by theframe-like bonding layer 404 a and moisture that passes through theframe-like bonding layer 404 a is adsorbed by the frame-like bondinglayer 404 b, whereby entry of moisture into the bonding layer 407, andfurthermore, the organic EL element 450 can be suppressed.

In Structural Example 4 light emission of the organic EL element 450 isextracted from the light-emitting device through the bonding layer 407.For this reason, the bonding layer 407 preferably has a more excellentlight-transmitting property than the frame-like bonding layers 404 a and404 b. Furthermore, the bonding layer 407 preferably has a higherrefractive index than the frame-like bonding layers 404 a and 404 b. Inaddition, it is preferred that the volume of the bonding layer 407 beless reduced by curing than those of the frame-like bonding layers 404 aand 404 b.

The light-emitting device described in Structural Example 4 can befabricated with high yield using the separating method described above.According to the separating method, the insulating layer 424, thetransistors, the organic EL element 450, and the like are formed overthe formation substrate, as a layer to be separated. Then, theinsulating layer 226, the coloring layer 432, the light-blocking layer431, and the like are formed over another formation substrate, as alayer to be separated. After the two formation substrates are bonded toeach other, the layers to be separated and the formation substrates areseparated from each other. Then, the layers to be separated and theflexible substrates are bonded to each other with a bonding layer, sothat the light-emitting device described in Structural Example 4 can befabricated.

According to the separating method described above, an insulating layerand transistors can be formed over a formation substrate at hightemperature. The use of the insulating layer 424, the insulating layer226, and the transistors formed at high temperature enables thelight-emitting device to have high reliability. The insulating layerswith an excellent gas barrier property (insulating layers 226 and 424)formed at high temperature can be provided over and below the organic ELelement 450. This can prevent impurities such as moisture from enteringthe organic EL element 450.

As described above, in Structural Example 4, the insulating layer 424,the insulating layer 226, and the frame-like bonding layers 404 a and104 b can suppress entry of impurities such as moisture from the frontsurface (display surface), the back surface (the surface opposite to thedisplay surface), and side surfaces of the light-emitting device intothe organic EL element 450. This increases the reliability of thelight-emitting device.

Note that although an organic EL element is used as the display elementhere, one embodiment of the present invention is not limited thereto.

Note that in one embodiment of the present invention, an active matrixmethod in which an active element (non-linear element) is included in apixel or a passive matrix method in which an active element is notincluded in a pixel can be used.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 4

In this embodiment, structures of an input/output device of embodimentsof the present invention will be described with reference to FIGS. 14Ato 14C and FIGS. 15A to 15C.

FIGS. 14A to 14C are projection views illustrating the structure of theinput/output device of one embodiment of the present invention.

FIG. 14A is the projection view illustrating an input/output device 500of one embodiment of the present invention. FIG. 14B is the projectionview illustrating the structure of a sensing unit 20U included in theinput/output device 500.

FIGS. 15A to 15C are cross-sectional views illustrating structures ofthe input/output device 500 of one embodiment of the present invention.

FIG. 15A is the cross-sectional view along Z1-Z2 of the input/outputdevice 500 of one embodiment of the present invention that isillustrated in FIGS. 14A to 14C.

Note that the input/output device 500 can also be referred to as a touchpanel.

<Structural Example 1 of Input/Output Device>

The input/output device 500 described in this embodiment includes aflexible input device 100 and a display portion 501 (see FIGS. 14A to14C). The flexible input device 100 is provided with a plurality ofsensing units 20U arranged in a matrix and including window portions 14that transmit visible light; a scan line G1 electrically connected tothe plurality of sensing units 20U arranged in the row direction (shownby an arrow R in FIG. 14A); a signal line DL electrically connected tothe plurality of sensing units 20U arranged in the column direction(shown by an arrow C in FIG. 14A); and a first flexible base 16supporting the sensing units 20U, the scan line G1, and the signal lineDL. The display portion 501 is provided with a plurality of pixels 502overlapping with the window portions 14 and arranged in a matrix; and asecond flexible base 510 supporting the pixels 502.

The sensing unit 20U includes a sensing element C overlapping with thewindow portions 14 and a sensing circuit 19 electrically connected tothe sensing element C (see. FIG. 14B).

The sensing element C includes an insulating layer 23 and a firstelectrode 21 and a second electrode 22 between which the insulatinglayer 23 is sandwiched (see FIG. 15A).

The sensing circuit 19 is supplied with a selection signal, and suppliesa sensing signal DATA in accordance with a change in the capacity of thesensing element C.

The scan line G1 can supply a selection signal. The signal line DL cansupply the sensing signal DATA. The sensing circuit 19 is provided so asto overlap with a gap between the window portions 14.

The input/output device 500 described in this embodiment furtherincludes a coloring layer between the sensing units 20U and the pixels502 overlapping with the window portions 14 of the sensing units 20U.

The input/output device 500 described in this embodiment includes theflexible input device 100 provided with the plurality of sensing units20U including the window portions 14 that transmit visible light and theflexible display portion 501 provided with the plurality of pixels 502overlapping with the window portions 14. In addition, the coloring layeris provided between the window portions 14 and the pixels 502.

With such a structure, the input/output device can supply a sensingsignal depending on a change in capacity and the positional data of thesensing unit that supplies the sensing signal, can display image dataassociated with the positional data of the sensing unit, and can bebent. Thus, the novel input/output device can be highly convenient orreliable.

The input/output device 500 may be provided with an FPC1 that issupplied with a signal supplied from the input device 100 and/or an FPC2that supplies a signal containing image data to the display portion 501.

The input/output device 500 may also be provided with a protective layer17 p that protects the input/output device 500 from suffering flawsand/or an antireflective layer 567 p that reduces the intensity ofexternal light the input/output device 500 reflects.

The input/output device 500 also includes a scan line driver circuit 503g that supplies a selection signal to the scan line of the displayportion 501 and a terminal 519 electrically connected to the FPC2 and awiring 511 that supplies a signal.

Individual components included in the input/output device 500 will bedescribed below. Note that these components cannot be clearlydistinguished and one component also serves as another component orinclude part of another component in some cases.

For example, the input device 100 provided with the coloring layeroverlapping with the plurality of window portions 14 also serves as acolor filter.

For example, the input/output device 500 where the input device 100overlaps with the display portion 501 serves as the input device 100 andthe display portion 501.

<<Overall Structure>>

The input/output device 500 includes the input device 100 and thedisplay portion 501 (see FIG. 14A).

<<Input Device 100>>

The input device 100 is provided with the plurality of sensing units 20Uand the flexible base 16 supporting the sensing units. For example, theplurality of sensing units 20U are arranged in a matrix of 40 rows and15 columns over the flexible base 16.

<<Window Portion 14, Coloring Layer, and Light-Blocking Layer BM>>

The window portion 14 can transmit visible light.

The coloring layer that transmits light of a predetermined color isprovided so as to overlap with the window portions 14. For example, acoloring layer CFB that transmits blue light, a coloring layer CFG thattransmits green light, or a coloring layer CFR that transmits red lightis provided (see FIG. 14B).

Note that besides the coloring layer that transmits blue light, thecoloring layer that transmits green light, and/or the coloring layerthat transmits red light, a coloring layer that transmits light of anyof a variety of colors such as white and yellow can also be provided.

A metal material, pigment, dye, or the like can be used for the coloringlayer.

The light-blocking layer BM is provided so as to surround the windowportions 14. The light-blocking layer BM transmits light less easilythan the window portions 14.

Carbon black, a metal oxide, a composite oxide containing a solidsolution of a plurality of metal oxides, or the like can be used for thelight-blocking layer BM.

The scan line G1, the signal line DL, a wiring VPI, a wiring RES, awiring VRES, and the sensing circuit 19 are provided so as to overlapwith the light-blocking layer BM.

Note that a light-transmitting overcoat layer can be provided so as tocover the coloring layer and the light-blocking layer BM.

<<Sensing Element C>>

The sensing element C includes the first electrode 21, the secondelectrode 22, and the insulating layer 23 between the first electrode 21and the second electrode 22 (see FIG. 15A).

The first electrode 21 is formed in, for example, an island shape so asto be separated from other regions. A layer that can be formed in thesame process as the first electrode 21 is particularly preferablyprovided in the proximity of the first electrode 21 so that the firstelectrode 21 is not recognized by a user of the input/output device 500.It is more preferred that the number of the window portions 14 providedin a gap between the first electrode 21 and the layer provided in theproximity of the first electrode 21 be as small as possible. It isparticularly preferred that the window portions 14 not be provided inthe gap.

The second electrode 22 is provided so as to overlap with the firstelectrode 21, and the insulating layer 23 is provided between the firstelectrode 21 and the second electrode 22.

For example, when a sensing target (specifically, a finger or the like)having a dielectric constant different from that of the air approachesthe first electrode 21 or the second electrode 22 of the sensing elementC placed in the air, the capacitance of the sensing element C ischanged. Thus, the sensing element C can be used as a proximity sensor.

For example, the capacitance of the sensing element C that can changeits form varies with the change in the form of the sensing element C.

Specifically, when a sensing target such as a finger touches the sensingelement C and a gap between the first electrode 21 and the secondelectrode 22 becomes small, the capacitance of the sensing element Cincreases. Thus, the sensing element C can be used as a contact sensor.

Alternatively, when the sensing element C is folded, the gap between thefirst electrode 21 and the second electrode 22 becomes small.Consequently, the capacitance of the sensing element C increases. Thus,the sensing element C can be used as a folding sensor.

The first electrode 21 and the second electrode 22 are formed using aconductive material.

For example, an inorganic conductive material, an organic conductivematerial, metal, conductive ceramics, or the like can be used for thefirst electrode 21 and the second electrode 22.

Specifically, a metal element selected from aluminum, chromium, copper,tantalum, titanium, molybdenum, tungsten, nickel, silver, and manganese;an alloy containing any of the above-described metal elements; an alloycontaining any of the above-described metal elements in combination orthe like can be used.

Alternatively, a conductive oxide such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used.

Alternatively, graphene or graphite can be used. A film containinggraphene can be formed, for example, by reducing a film containinggraphene oxide. As a reducing method, a method using heat, a methodusing a reducing agent, or the like can be employed.

Alternatively, a conductive macromolecule can be used.

<<Sensing Circuit 19>>

The sensing circuit 19 includes, for example, transistors M1 to M3. Thesensing circuit 19 also includes wirings that supply power supplypotentials and signals, such as the wiring VPI, a wiring CS, the scanline G1, the wiring RES, the wiring VRES, and the signal line DL. Notethat the specific configuration of the sensing circuit 19 will bedescribed in detail in Embodiment 5.

Note that the sensing circuit 19 may be provided so as not to overlapwith the window portions 14. For example, the wirings are provided so asnot to overlap with the window portions 14, whereby an object on oneside of the sensing unit 20U can be easily viewed from the other side.

The transistors M1 to M3 can be formed in the same process, for example.

The transistor M1 includes a semiconductor layer. For example, a Group14 element, a compound semiconductor, or an oxide semiconductor can beused for the semiconductor layer. Specifically, a silicon-containingsemiconductor, a gallium arsenide-containing semiconductor, anindium-containing oxide semiconductor, or the like can be used.

Note that the structure of the transistor including a semiconductorlayer using an oxide semiconductor will be described in detail inEmbodiment 5.

A conductive material can be used for the wirings.

For example, an inorganic conductive material, an organic conductivematerial, metal, conductive ceramics, or the like can be used for thewirings. Specifically, the materials that can be used for the firstelectrode 21 and the second electrode 22 can be used.

A metal material such as aluminum, gold, platinum, silver, nickel,titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, orpalladium or an alloy material containing any of the metal materials canbe used for the scan line G1, the signal line DL, the wiring VPI, thewiring RES, and the wiring VRES.

Films formed over the base 16 may be processed into the sensing circuit19.

Alternatively, the sensing circuit 19 formed on any other base may betransferred to the base 16.

Note that a manufacturing method of a sensing circuit will be describedin detail in Embodiment 5.

<<Base 16>>

As a material of the base 16, an organic material, an inorganicmaterial, or a composite material of an organic material and aninorganic material can be used.

The base 16 can be formed using a material with a thickness in the rangefrom 5 μm to 2500 μm, preferably from 5 μm to 680 μm, more preferablyfrom 5 μm to 170 μm, more preferably from 5 μm to 45 μm, more preferablyfrom 5 μm to 45 μm, more preferably from 8 μm to 25 μm.

Materials with which passage of impurities is inhibited can be favorablyused in the base 16. For example, materials with a vapor permeability oflower than or equal to 10⁻⁵ g/m²·day, preferably lower than or equal to10⁻⁶ g/m²·day can be favorably used.

The base 16 can be favorably funned using a material whose coefficientof linear expansion is substantially equal to that of the second base510. For example, the coefficient of linear expansion of the material ispreferably lower than or equal to 1×10⁻³/K, more preferably lower thanor equal to 5×10⁻⁵/K, and still more preferably lower than or equal to1×10⁻⁵/K.

Examples of the material of the base 16 include organic materials suchas a resin, a resin film, and a plastic film.

Examples of the material of the base 16 include inorganic materials suchas a metal plate and a thin glass plate with a thickness of more than orequal to 10 μm and less than or equal to 50 μm.

Examples of the material of the base 16 include composite materials suchas resin films to which a metal plate, a thin glass plate, or a film ofan inorganic material is attached using a resin layer.

Examples of the material of the base 16 include composite materials suchas resins or resin films into which a fibrous or particulate metal,glass, or inorganic material is dispersed.

For example, a thermosetting resin or an ultraviolet curable resin canbe used for a resin layer.

Specifically, a resin film or resin plate of polyester, polyolefin,polyimide, polyimide, polycarbonate, an acrylic resin, or the like canbe used.

Alternatively, as glass, non-alkali glass, soda-lime glass, potashglass, crystal glass, or the like can be used.

Alternatively, a metal oxide film, a metal nitride film, a metaloxynitride film, or the like can be used. For example, silicon oxide,silicon nitride, silicon oxynitride, an alumina film, or the like can beused.

Alternatively, SUS, aluminum, or the like provided with an opening canbe used.

Alternatively, a resin such as an acrylic resin, a urethane resin, anepoxy resin, or a resin having a siloxane bond can be used.

For example, a stack in which a flexible base 16 b, a barrier film 16 athat prevents diffusion of impurities, and a resin layer 16 c that bondsthe barrier film 16 a to the base 16 b are stacked can be favorably usedfor the base 16 (see FIG. 15A).

A film including a layered material in which a 600-nm silks oxynitridefilm and a 200-nm silicon nitride film are stacked can be specificallyused as the barrier film 16 a.

Alternatively, a film including a layered material of a 600-nm-thicksilicon oxynitride film, a 200-nm-thick silicon nitride film, a200-nm-thick oxynitride film, a 140-nm-thick silicon nitride oxide film,and a 100-nm-thick silicon oxynitride film stacked in this order can beused as the barrier film 16 a.

Specifically, a resin film, resin plate, or a stack of polyester,polyolefin, polyamide, polyimide, polycarbonate, an acrylic resin, orthe like can be used as the base 16 b.

For example, materials that contain polyester, polyolefin, polyamide(e.g., nylon and aramid), polyimide, polycarbonate, or a resin having anacrylic bond, an urethane bond, an epoxy bond, or a siloxane bond can beused for the resin layer 16 c.

<<Protective Base 17, Protective Layer 17 p>>

A flexible protective base 17 and/or the protective layer 17 p can beprovided. The flexible protective base 17 or the protective layer 17 pprotects the input device 100 from suffering flaws.

For example, a resin film, resin plate, stack, or the like of polyester,polyolefin, polyamide, polyimide, polycarbonate, an acrylic resin, orthe like can be used as the protective base 17.

For example, a hard coat layer or a ceramic coat layer can be used asthe protective layer 17 p. Specifically, a layer containing a UV curableresin or aluminum oxide may be formed so as to overlap with the secondelectrode 22.

<<Display Portion 501>>

The display portion 501 includes the plurality of pixels 502 arranged ina matrix (see FIG. 14C).

For example, the pixel 502 includes a sub-pixel 502B, a sub-pixel 502G,and a sub-pixel 502R. Each sub-pixel includes a display element and apixel circuit that drives the display element.

Note that the sub-pixel 502B in the pixel 502 is positioned so as tooverlap with the coloring layer CFB, the sub-pixel 502G is positioned soas to overlap with the coloring layer CFG, and the sub-pixel 502R ispositioned so as to overlap with the coloring layer CFR.

In this embodiment, an example of using an organic electroluminescentelement that emits white light as a display element will be described;however, the display element is not limited to such an element.

For example, organic electroluminescent elements that emit light ofdifferent colors may be included in sub-pixels so that the light ofdifferent colors can be emitted from the respective sub-pixels.

In the display portion, an active matrix method in which an activeelement is included in a pixel or a passive matrix method in which anactive element is not included in a pixel can be used.

In an active matrix method, as an active element (a non-linear element),not only a transistor but also various active elements (non-linearelements) can be used. For example, an MIM (metal insulator metal), aTFD (thin film diode), or the like can also be used. Since such anelement has a small number of manufacturing steps, manufacturing costcan be reduced or yield can be improved. Alternatively, since the sizeof the element is small, the aperture ratio can be improved, so thatpower consumption can be reduced or higher luminance can be achieved.

As a method other than the active matrix method, the passive matrixmethod in which an active element (a non-linear element) is not used canalso be used. Since an active element (a non-linear element) is notused, the number of manufacturing steps is small, so that manufacturingcost can be reduced or yield can be improved. Alternatively, since anactive element (a non-linear element) is not used, the aperture ratiocan be improved, so that power consumption can be reduced or higherluminance can be achieved, for example.

<<Second Base 510>>

A flexible material can be used for the second base 510. For example, amaterial that can be used for the base 16 can be used for the secondbase 510.

A stack in which a flexible base 510 b, a barrier film 510 a thatprevents diffusion of impurities, and a resin layer 510 c that bonds thebarrier film 510 a, to the base 510 b are stacked can be favorably usedfor the second base 510, for example (see FIG. 15A).

<<Sealant>>

The sealant 560 bonds the base 16 and the second base 510 together. Thesealant 560 has a refractive index higher than that of the air. In thecase of extracting light to the sealant 560 side, the sealant 560 has afunction of optical adhesion.

The pixel circuits and the light-emitting elements (e.g., alight-emitting element 550R) are provided between the second base 510and the base 16.

<<Pixel Structure>>

The sub-pixel 502R includes a light-emitting module 580R.

The sub-pixel 502R includes the first light-emitting element 550R andthe pixel circuit that can supply power to the first light-emittingelement 550R and includes a transistor 502 t. The light-emitting module580R includes the light-emitting element 550R and an optical element(e.g., the coloring layer CFR).

The first light-emitting element 550R includes a lower electrode, anupper electrode, and a layer containing a light-emitting organiccompound between the lower electrode and the upper electrode.

The light-emitting module 580R includes the coloring layer CFR on thelight extraction side. The coloring layer transmits light with aparticular wavelength and is, for example, a layer that selectivelytransmits red, green, or blue light. Note that other sub-pixels may beprovided so as to overlap with the window portions, which are notprovided with the coloring layers, so that light from the light-emittingelement can be emitted without passing through the coloring layers.

In the case where the sealant 560 is provided on the light extractionside, the sealant 560 is in contact with the light-emitting element 550Rand the coloring layer CFR.

The coloring layer CFR is positioned in a region overlapping with thelight-emitting element 550R. Accordingly, part of light emitted from thelight-emitting element 550R passes through the coloring layer CFR and isemitted to the outside of the light-emitting module 580R as indicated byan arrow in FIG. 15A.

The light-blocking layer BM is located so as to surround the coloringlayer (e.g., the coloring layer CFR).

<<Structure of Pixel Circuit>>

An insulating film 521 covering the transistor 502 t included in thepixel circuit is provided. Note that the insulating film 521 can be usedas a layer for planarizing unevenness due to the pixel circuit. Alayered film including a layer that can prevent diffusion of impuritiescan be used as the insulating film 521. This can prevent the reliabilityof the transistor 502 t or the like from being lowered by diffusion ofimpurities.

The lower electrode is provided over the insulating film 521, and apartition wall 528 is provided over the insulating film 521 so as tooverlap with an end portion of the lower electrode.

The lower electrode is included in the light-emitting element (e.g., thelight-emitting element 550R); the layer containing a light-emittingorganic compound is provided between the upper electrode and the lowerelectrode. The pixel circuit supplies power to the light-emittingelement.

Furthermore, a spacer that adjusts a gap between the base 16 and thesecond base 510 is provided over the partition wall 528.

<<Configuration of Scan Line Driver Circuit>>

A scan line driver circuit 503 g(1) includes a transistor 503 t and acapacitor 503 c. Note that transistors used in the pixel circuit andtransistors used in the driver circuit can be formed in the same processand over the same substrate.

<<Converter CONV>>

Any of various circuits that can convert the sensing signal DATAsupplied from the sensing unit 20U and supply a signal obtained by theconversion to the FPC1 can be used for a converter CONV (see FIG. 14Aand FIG. 15A).

For example, a transistor M4 can be used in the converter CONV.

<<Other Components>>

The display portion 501 includes an anti-reflective layer 567 ppositioned in a region overlapping with pixels. As the anti-reflectivelayer 567 p, a circular polarizing plate can be used, for example.

The display portion 501 includes the wirings 511 through which signalsare supplied. The wirings 511 are provided with the terminal 519. Notethat the FPC2 through which a signal such as an image signal or asynchronization signal can be supplied is electrically connected to theterminal 519.

Note that a printed wiring board (PWB) may be attached to the FPC2.

The display portion 501 includes wirings such as scan lines, signallines, and power supply lines. Any of various conductive films can beused for the wirings.

Specifically, a metal element selected from aluminum, chromium, copper,tantalum, titanium, molybdenum, tungsten, nickel, yttrium, zirconium,silver, and manganese; an alloy containing any of the above-describedmetal elements; an alloy containing any of the above-described metalelements in combination; or the like can be used. In particular, one ormore elements selected from aluminum, chromium, copper, tantalum,titanium, molybdenum, and tungsten are preferably contained. Inparticular, an alloy of copper and manganese is suitably used inmicrofabrication with the use of a wet etching method.

Specifically, a two-layer structure in which a titanium film is stackedover an aluminum film, a two-layer structure in which a titanium film isstacked over a titanium nitride film, a two-layer structure in which atungsten film is stacked over a titanium nitride film, a two-layerstructure in which a tungsten film is stacked over a tantalum nitridefilm or a tungsten nitride film, a three-layer structure in which atitanium film, an aluminum film, and a titanium film are stacked in thisorder, or the like can be used.

Specifically, a layered structure in which a film of an element selectedfrom titanium, tantalum, tungsten, molybdenum, chromium, neodymium, andscandium, an alloy film containing some of these elements, or a nitridefilm of any of these elements is stacked over an aluminum film can beused.

Alternatively, a light-transmitting conductive material containingindium oxide, tin oxide, or zinc oxide may be used.

<Modification Example of Display Portion>

Any of various kinds of transistors can be used in the display portion501.

A structure of the case of using bottom-gate transistors in the displayportion 501 is illustrated in FIGS. 15A and 15B.

For example, a semiconductor layer containing an oxide semiconductor,amorphous silicon, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 15A.

For example, a semiconductor layer containing polycrystalline siliconthat is obtained by crystallization process such as laser annealing canbe used in the transistor 502 t and the transistor 503 t illustrated inFIG. 15B.

A structure of the case of using top-gate transistors in the displayportion 501 is illustrated in FIG. 15C.

For example, a semiconductor layer containing polycrystalline silicon, asingle crystal silicon film that is transferred from a single crystalsilicon substrate, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 15C.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

Embodiment 5

In this embodiment, the configuration and a driving method of a sensingcircuit that can be used for the sensing unit in the input/output deviceof embodiments of the present invention will be described with referenceto FIGS. 16A, 16B1, and 16B2.

FIGS. 16A, 16B1, and 16B2 illustrate the configuration and drivingmethods of the sensing circuit 19 and the converter CONV of oneembodiment of the present invention.

FIG. 16A is a circuit diagram illustrating the configuration of thesensing circuit 19 and the converter CONV of one embodiment of thepresent invention. FIGS. 16B1 and 16B2 are timing charts illustratingthe driving methods.

The sensing circuit 19 of one embodiment of the present inventionincludes the first transistor M1 whose gate is electrically connected tothe first electrode 21 of the sensing element C and whose firstelectrode is electrically connected to the wiring VPI that can supply aground potential, for example (see FIG. 16A).

The sensing circuit 19 may further include the second transistor M2whose gate is electrically connected to the scan line G1 that can supplya selection signal, whose first electrode is electrically connected to asecond electrode of the first transistor M1, and whose second electrodeis electrically connected to the signal line DL that can supply thesensing signal DATA, for example.

The sensing circuit 19 may further include the third transistor M3 whosegate is electrically connected to the wiring RES that can supply a resetsignal, whose first electrode is electrically connected to the firstelectrode 21 of the sensing element C, and whose second electrode iselectrically connected to, for example, the wiring VRES that can supplya ground potential.

The capacitance of the sensing element C varies, for example, when anobject gets closer to the first electrode 21 or the second electrode 22or when a gap between the first electrode 21 and the second electrode 22is changed. Thus, a sensor 20B can supply the sensing signal DATA inaccordance with a change in the capacitance of the sensing element C.

The sensor 20B is provided with the wiring CS that can supply a controlsignal for controlling the potential of the second electrode 22 of thesensing element C.

Note that a portion where the first electrode 21 of the sensing elementC, the gate of the first transistor M1, and the first electrode of thethird transistor are electrically connected is referred to as a node A.

The wiring VRES and the wiring VPI can supply, for example, a groundpotential. A wiring VPO and a wiring BR can supply, for example, a highpower supply potential.

The wiring RES can supply a reset signal. The scan line G1 can supply aselection signal. The wiring CS can supply a control signal forcontrolling the potential of the second electrode 22 of the sensingelement C.

The signal line DL can supply the sensing signal DATA. A terminal OUTcan supply a signal obtained by conversion based on the sensing signalDATA.

Note that any of various circuits that can convert the sensing signalDATA and supply a signal obtained by the conversion to the terminal OUTcan be used for the converter CONV. The converter CONV may beelectrically connected to the sensing circuit 19 to form a sourcefollower circuit, a current mirror circuit, or the like, for example.

Specifically, a source follower circuit can be formed using theconverter CONV including the transistor M4 (see FIG. 16A). Note that thetransistor M4 may be formed in the same process as the first to thirdtransistors M1 to M3.

The transistors M1 to M3 each include a semiconductor layer. Forexample, a Group 4 element, a compound semiconductor, or an oxidesemiconductor can be used for the semiconductor layer. Specifically, asilicon-containing semiconductor, a gallium arsenide-containingsemiconductor, an indium-containing oxide semiconductor, or the like canbe used.

Note that the structure of a transistor using an oxide semiconductor fora semiconductor layer will be described in detail in Embodiment 5.

<Driving Method of Sensing Circuit 19>

The driving method of the sensing circuit 19 will be described.

<<First Step>>

In a first step, after the third transistor is turned on, a reset signalfor turning off the third transistor is supplied to the gate of thethird transistor, so that the potential of the first electrode of thesensing element C is set to a predetermined potential (see Period T1 inFIG. 16B1).

Specifically, the wiring RES is made to supply a reset signal. The thirdtransistor supplied with the reset signal renders the potential of thenode A a ground potential, for example (see FIG. 16A).

<<Second Step>>

In a second step, a selection signal for turning on the secondtransistor M2 is supplied to the gate of the second transistor M2, sothat the second electrode of the first transistor is electricallyconnected to the signal line DL.

Specifically, the scan line G1 is made to supply a selection signal. Thesecond transistor M2 supplied with the selection signal electricallyconnects the second electrode of the first transistor and the signalline DL (see Period T2 in FIG. 16B1).

<<Third Step>>

In a third step, a control signal is supplied to the second electrode ofthe sensing element C, and a control signal and the potential thatvaries depending on the capacitance of the sensing element C aresupplied to the gate of the first transistor M1.

Specifically, a rectangular control signal is supplied to the wiring CS.The sensing element C whose second electrode 22 is supplied with therectangular control signal increases the potential of the node A inaccordance with the capacitance of the sensing element C (see the latterpart of Period 12 in FIG. 16B1).

For example, when the sensing element C is placed in the air and anobject having a higher dielectric constant than the air is placed in theproximity of the second electrode 22 of the sensing element C, theapparent capacitance of the sensing element C is increased.

Thus, a change in the potential of the node A caused by the rectangularcontrol signal is smaller than that when an object having a higherdielectric constant than the air is not placed in the proximity of thesecond electrode 22 of the sensing element C (see a solid line in FIG.16B2).

<<Fourth Step>>

In a fourth step, a signal caused by a change in the potential of thegate of the first transistor M1 is supplied to the signal line DL.

For example, a change in current caused by a change in the potential ofthe gate of the first transistor M1 is supplied to the signal line DL.

The converter CONV converts a change in current flowing through thesignal line DL into a voltage change and supplies the voltage change.

<<Fifth Step>>

In a fifth step, a selection signal for turning off the secondtransistor is supplied to the gate of the second transistor.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

Embodiment 6

In this embodiment, an example in which a laminated lithium-ionsecondary battery is fabricated with the use of a film as an exteriorbody will be described. The laminated lithium-ion secondary batterycorresponds to the battery 117 illustrated in FIG. 4 of Embodiment 1.

First, a sheet made of a flexible material is prepared. As the sheet, astacked body; a metal film provided with an adhesive layer (alsoreferred to as a heat-seal layer) or sandwiched between adhesive layersis used. As the adhesive layer, a heat-seal resin film containing, e.g.,polypropylene or polyethylene is used. In this embodiment, a metalsheet, specifically, aluminum foil whose top surface is provided, with anylon resin and whose bottom surface is provided with a stack includingan acid-proof polypropylene film and a polypropylene film is used as thesheet. This sheet is cut to obtain a film 31 illustrated in FIG. 19A.

Then, the film 31 may be embossed to form unevenness so that the patterncan be visually recognized. Although an example where the sheet is cutand then embossing is performed is described here, the order is notparticularly limited; embossing may be performed before cutting thesheet and then the sheet may be cut. Alternatively, the sheet may be cutafter thermocompression bonding is performed with the sheet bent.

Note that embossing refers to processing for forming unevenness on asurface of a film by bringing an embossing roll whose surface hasunevenness into contact with the film with pressure. The embossing rollis a roll whose surface is patterned. The embossing roll is notnecessarily used, and an embossing plate may be used. Furthermore,embossing is not necessarily employed, and any method that allowsformation of a relief on part of the film is employed.

In this embodiment, both surfaces of a film 31 are provided withunevenness to have patterns, and the film 31 is folded in half so thattwo end portions each including two of the four corners overlap witheach other, and is sealed on three sides with an adhesive layer.

Then, the film 31 is folded, whereby a state illustrated in FIG. 19A isproduced.

A positive electrode current collector 32, a separator 33, and anegative electrode current collector 34 that are stacked and included ina secondary battery as illustrated in FIG. 19B are prepared. Thepositive electrode current collector 32 and the negative electrodecurrent collector 34 can each be formed using a highly conductivematerial that is not alloyed with a carrier ion of, for example,lithium, such as a metal typified by stainless steel, gold, platinum,zinc, iron, nickel, copper, aluminum, titanium, and tantalum or an alloythereof. Alternatively, an aluminum alloy to which an element whichimproves heat resistance, such as silicon, titanium, neodymium,scandium, and molybdenum, is added can be used. Still alternatively, ametal element which forms silicide by reacting with silicon can be used.Examples of the metal element which forms silicide by reacting withsilicon include zirconium, titanium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum, tungsten, cobalt, nickel, and the like.The current collectors can each have a foil-like shape, a plate-likeshape (sheet-like shape), a net-like shape, a cylindrical shape, a coilshape, a punching-metal shape, an expanded-metal shape, or the like asappropriate. The current collectors each preferably have a thickness of10 μm to 30 μm inclusive. Note that the example where one combination ofthe positive electrode current collector 32, the separator 33, and thenegative electrode current collector 34 that are stacked is packed in anexterior body is illustrated here for simplicity. To increase thecapacity of a secondary battery, a plurality of combinations may bestacked and packed in an exterior body. The separator 33 in thesecondary battery may be used either by being folded or in a bag-likeform in the secondary battery.

In addition, two lead electrodes 36 with sealing layers 35 illustratedin FIG. 19C are prepared. The lead electrodes 36 are each also referredto as a lead terminal and provided in order to lead a positive electrodeor a negative electrode of a secondary battery to the outside of anexterior film.

Then, one of the lead electrodes is electrically connected to aprotruding portion of the positive electrode current collector 32 byultrasonic welding or the like. The other lead electrode is electricallyconnected to a protruding portion of the negative electrode currentcollector 34 by ultrasonic welding or the like.

Then, two sides of the film 31 are sealed by thermocompression bonding,and one side is left open for introduction of an electrolytic solution.In thermocompression bonding, the sealing layers 35 provided on the leadelectrodes are also melted, thereby fixing the lead electrodes and thefilm 31 to each other. After that, in a reduced-pressure atmosphere oran inert atmosphere, a desired amount of electrolytic solution isintroduced to the inside of the film 31 in the form of a bag. Lastly,the outer edge of the film that has not been subjected tothermocompression bonding and is left open is sealed bythermocompression bonding.

In this manner, a secondary battery 40 illustrated in FIG. 19D can befabricated.

In the obtained secondary battery 40, the surface of the film 31 servingas an exterior body has a pattern including unevenness. An edge regionindicated by a dotted line in FIG. 19D is a thermocompression-bondedregion 37. A surface of the thermocompression-bonded region 37 also hasa pattern including unevenness. Although the unevenness in thethermocompression-bonded region 37 is smaller than that in a centerportion, it can relieve stress applied when the secondary battery isbent. Such a structure as can relieve a strain caused by stress canprevent the secondary battery (e.g., an exterior body) from beingdamaged when changed in form by being bent, for example, achievinglong-time reliability.

FIG. 19E illustrates an example of a cross section taken alongdashed-dotted line A-B in FIG. 19D.

As illustrated in FIG. 19E, unevenness of the film 31 is differentbetween a region overlapping with the positive electrode currentcollector 32 and the thermocompression-bonded region 37. As illustratedin FIG. 19E, the positive electrode current collector 32, a positiveelectrode active material layer 38, the separator 33, a negativeelectrode active material layer 39, and the negative electrode currentcollector 34 are stacked in this order and placed inside the folded film31, an end portion is sealed with an adhesive layer 41, and the otherspace is provided with an electrolytic solution 42.

Examples of positive electrode active materials that can be used for thepositive electrode active material layer 38 include a composite oxidewith an olivine structure, a composite oxide with a layered rock-saltstructure, and a composite oxide with a spinel structure. Specifically,a compound such as LiFeO₂, LiCoO₂, LiNiO₂, LiMn₂O₄, V₂O₅, Cr₂O₅, or MnO₂can be used.

Alternatively, a complex material (LiMPO₄ (general formula) (M is one ormore of Fe(II), Mn(II), Co(II), and Ni(II))) can be used. Typicalexamples of the general formula LiMPO₄ which can be used as a materialare lithium compounds such as LiFePO₄, LiNiPO₄, LiCoPO₄, LiMnPO₄,LiFe_(a)Ni_(b)PO₄, LiFe_(a)Co_(b)PO₄, LiFe_(a)Mn_(b)PO₄,LiNi_(a)Co_(b)PO₄, LiNi_(a)Mn_(b)PO₄ (a+b≤1, 0<a<1, and 0<b<1),LiFe_(c)Ni_(d)Co_(e)PO₄, LiFe_(c)Ni_(d)Mn_(e)PO₄,LiNi_(c)Co_(d)Mn_(e)PO₄ (c+d+e≤1, 0<c<1, 0<d<1, and 0<e<1), andLiFe_(f)Ni_(g)Co_(h)Mn_(i)PO₄ (f+g+h+i≤1, 0<f<1, 0<g<1, 0<h<1, and0<i<1).

Alternatively, a complex material such as Li_((2-f))MSiO₄ (generalformula) (M is one or more of Fe(II), Mn(II), Co(II), and Ni(II); 0≤j≤2)may be used. Typical examples of the general formula Li_((2-f))MSiO₄which can be used as a material are lithium compounds such asLi_((2-f))FeSiO₄, Li_((2-f))NiSiO₄, Li_((2-f))CoSiO₄, Li_((2-f))MnSiO₄,Li_((2-f))Fe_(k)Ni_(l)SiO₄, Li_((2-f))Fe_(k)Co_(l)SiO₄,Li_((2-f))Fe_(k)Mn_(l)SiO₄, Li_((2-f))Ni_(k)Co_(l)SiO₄,Li_((2-f))Ni_(k)Mn_(l)SiO₄ (k+l≤1, 0<k<1, and 0<l<1),Li_((2-f))Fe_(m)Ni_(n)Co_(q)SiO₄, Li_((2-f))Fe_(m)Ni_(n)Mn_(q)SiO₄,Li_((2-f))Ni_(m)Co_(n)Mn_(q)SiO₄ (m+n+q≤1, 0<m<1, 0<n<1, and 0<q<1), andLi_((2-f))Fe_(r)Ni_(s)Co_(t)Mn_(u)SiO₄ (r+s+t+u≤1, 0<r<1, 0<s<1, 0<t<1,and 0<u<1).

Still alternatively, a nasicon compound expressed by A_(x)M₂(XO₄)₃(general formula) (A=Li, Na, or Mg, M=Fe, Mn, Ti, V, Nb, or Al, X=S, P,Mo, W As, or Si) can be used for the positive electrode active material.Examples of the nasicon compound are Fe₂(MnO₄)₃, Fe₂(SO₄)₃, andLi₃Fe₂(PO₄)₃. Further alternatively, a compound expressed by Li₂MPO₄F,Li₂MP₂O₇, or Li₅MO₄ (general formula) (M=Fe or Mn), a perovskitefluoride such as NaFeF₃ and FeF₃, a metal chalcogenide (a sulfide, aselenide, or a telluride) such as TiS₂ and MoS₂, an oxide with aninverse spinel structure such as LiMVO₄, a vanadium oxide (V₂O₅, V₆O₁₃,LiV₃O₈, or the like), a manganese oxide, an organic sulfur compound, orthe like can be used as the positive electrode active material.

In the case where carrier ions are alkali metal ions other than lithiumions, or alkaline-earth metal ions, a material containing an alkalimetal (e.g., sodium and potassium) or an alkaline-earth metal (e.g.,calcium, strontium, barium, beryllium, and magnesium) instead of lithiummay be used as the positive electrode active material.

As the separator 33, an insulator such as cellulose (paper),polyethylene with pores, polypropylene with pores, polyimide with pores,or a ceramic with pores can be used.

As an electrolyte of the electrolytic solution 42, a material thatcontains carrier ions is used. Typical examples of the electrolyte arelithium salts such as LiPF₆, LiClO₄, LiAsF₆, LiBF₄, LiCF₃SO₃,Li(CF₃SO₂)₂N, and Li(C₂F₅SO₂)₂N. One of these electrolytes may be usedalone, or two or more of them may be used in an appropriate combinationand in an appropriate ratio.

Note that when carrier ions are alkali metal ions other than lithiumions or alkaline-earth metal ions, instead of lithium in the abovelithium salts, an alkali metal (e.g., sodium and potassium), analkaline-earth metal (e.g., calcium, strontium, barium, beryllium, andmagnesium) may be used for the electrolyte.

As a solvent of the electrolytic solution, a material with the carrierion mobility is used. As the solvent of the electrolytic solution, anaprotic organic solvent is preferably used. Typical examples of aproticorganic solvents include ethylene carbonate (EC), propylene carbonate,dimethyl carbonate, diethyl carbonate (DEC), γ-butyrolactone,acetonitrile, dimethoxyethane, tetrahydrofuran, and the like, and one ormore of these materials can be used. When a gelled high-molecularmaterial is used as the solvent of the electrolytic solution, safetyagainst liquid leakage and the like is improved. Furthermore, thestorage battery can be thinner and more lightweight. Typical examples ofgelled high-molecular materials include a silicone gel, an acrylic gel,an acrylonitrile gel, polyethylene oxide, polypropylene oxide, afluorine-based polymer, and the like. Alternatively, the use of one ormore kinds of ionic liquids (room temperature molten salts) which havefeatures of non-flammability and non-volatility as a solvent of theelectrolytic solution can prevent the storage battery from exploding orcatching fire even when the storage battery internally shorts out or theinternal temperature increases owing to overcharging and others. Anionic liquid is a salt in the liquid state and has high ion mobility(conductivity). An ionic liquid contains a cation and an anion. Examplesof ionic liquids include an ionic liquid containing anethylmethylimidazolium (EMI) cation and an ionic liquid containing anN-methyl-N-propylpiperidinium (PP₁₃) cation.

Instead of the electrolytic solution, a solid electrolyte including aninorganic material such as a sulfide-based inorganic material or anoxide-based inorganic material, or a solid electrolyte including amacromolecular material such as a polyethylene oxide (PEO)-basedmacromolecular material may alternatively be used. When the solidelectrolyte is used, a separator and a spacer are not necessary.Furthermore, the battery can be entirely solidified; therefore, there isno possibility of liquid leakage and thus the safety of the battery isdramatically increased.

A material with which lithium can be dissolved and precipitated or amaterial into and from which lithium ions can be inserted and extractedcan be used for a negative electrode active material of the negativeelectrode active material layer 39; for example, a lithium metal, acarbon-based material, an alloy-based material, or the like can be used.

The lithium metal is preferable because of its low redox potential(3.045 V lower than that of a standard hydrogen electrode) and highspecific capacity per unit weight and per unit volume (3860 mAh/g and2062 mAh/cm³).

Examples of the carbon-based material include graphite, graphitizingcarbon (soft carbon), non-graphitizing carbon (hard carbon), a carbonnanotube, graphene, carbon black, and the like.

Examples of the graphite include artificial graphite such as meso-carbonmicrobeads (MCMB), coke-based artificial graphite, or pitch-basedartificial graphite and natural graphite such as spherical naturalgraphite.

Graphite has a low potential substantially equal to that of a lithiummetal (0.1 V to 0.3 V vs. Li/Li⁺) when lithium ions are intercalatedinto the graphite (while a lithium-graphite intercalation compound isformed). For this reason, a lithium-ion secondary battery can have ahigh operating voltage. In addition, graphite is preferable because ofits advantages such as relatively high capacity per unit volume, smallvolume expansion, low cost, and safety greater than that of a lithiummetal.

For the negative electrode active material, a material which enablescharge-discharge reactions by an alloying reaction and a dealloyingreaction with lithium can be used. In the case where carrier ions arelithium ions, a material containing at least one of Al, Si, Ge, Sn, Pb,Sb, Bi, Ag, Au, Zn, Cd, In, Ga, and the like can be used as such amaterial, for example. Such elements have higher capacity than carbon.In particular, silicon has a significantly high theoretical capacity of4200 mAh/g. For this reason, silicon is preferably used as the negativeelectrode active material. Examples of the material using such elementsinclude Mg₂Si, Mg₂Ge, Mg₂Sn, SnS₂, V₂Sn₃, FeSn₂, CoSn₂, Ni₃Sn₂, Cu₆Sn₅,Ag₃Sn, Ag₃Sb, Ni₂MnSb, CeSb₃, LaSn₃, La₃Co₂Sn₇, CoSb₃, InSb, SbSn, andthe like.

Alternatively, for the negative electrode active materials, an oxidesuch as SiO, SnO, SnO₂, titanium oxide (e.g., TiO₂), lithium titaniumoxide (e.g., Li₄Ti₅O₁₂), lithium-graphite intercalation compound (e.g.,Li_(x)C₆), niobium oxide (e.g., Nb₂O₅), tungsten oxide (e.g., WO₂), ormolybdenum oxide (e.g., MoO₂) can be used.

Still alternatively, for the negative electrode active materials,L_(3-x)M_(x)N (M=Co, Ni, or Cu) with a Li₃N structure, which is anitride containing lithium and a transition metal, can be used. Forexample, Li_(2.6)Co_(0.4)N₃ is preferable because of high charge anddischarge capacity (900 mAh/g and 1890 mAh/cm³).

A nitride containing lithium and a transition metal is preferably used,in which case lithium ions are contained in the negative electrodeactive materials and thus the negative electrode active materials can beused in combination with a material for a positive electrode activematerial which does not contain lithium ions, such as V₂O₅ or Cr₃O₈. Inthe case of using a material containing lithium ions as a positiveelectrode active material, the nitride containing lithium and atransition metal can be used for the negative electrode active materialby extracting the lithium ions contained in the positive electrodeactive material in advance.

Alternatively, a material which causes a conversion reaction can be usedfor the negative electrode active materials; for example, a transitionmetal oxide which does not cause an alloy reaction with lithium, such ascobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may beused. Other examples of the material which causes a conversion reactioninclude oxides such as Fe₂O₃, CuO, Cu₂O, RuO₂, and Cr₂O₃, sulfides suchas CoS_(0.89), NiS, and CuS, nitrides such as Zn₃N₂, Cu₃N, and Ge₃N₄,phosphides such as NiP₂, FeP₂, and CoP₃, and fluorides such as FeF₃ andBiF₃. Note that any of the fluorides can be used as a positive electrodeactive material because of its high potential.

The negative electrode active material layer 39 may further include abinder for increasing adhesion of active materials, a conductiveadditive for increasing the conductivity of the negative electrodeactive material layer 39, and the like in addition to the above negativeelectrode active materials.

In the secondary battery, for example, the separator 33 has a thicknessof approximately 25 μm, the positive electrode current collector 32 hasa thickness of approximately 20 μm to 40 μm, the positive electrodeactive material layer 38 has a thickness of approximately 100 μm, thenegative electrode active material layer 39 has a thickness ofapproximately 100 μm, and the negative electrode current collector 34has a thickness of approximately 20 μm to 40 μm. The film 31 has athickness of 0.113 mm. Although the adhesive layer 41 is only partlyillustrated in FIG. 19E, only a thermocompression-bonded portion of alayer made of polypropylene which is provided on the surface of the film31 is the adhesive layer 41.

FIG. 19E illustrates an example where the bottom side of the film 31 isfixed and pressure bonding is performed. In this case, the top side isgreatly bent and a step is formed. Thus, when a plurality ofcombinations of the above stacked layers (e.g., eight or morecombinations) is provided inside the folded film 31, the step is largeand the top side of the film 31 might be too stressed. Furthermore, anend face of the top side of the film might be misaligned with an endface of the bottom side of the film. To prevent misalignment of the endfaces, a step may also be provided for the bottom side of the film andpressure bonding may be performed so that the thermocompression-bondedregion 37 is positioned at a center portion in the thickness directionof the secondary battery, whereby stress is uniformly applied.

Here, a current flow in charging a secondary battery will be describedwith reference to FIG. 19F. When a secondary battery using lithium isregarded as a closed circuit, lithium ions transfer and a current flowsin the same direction. Note that in the secondary battery using lithium,an anode and a cathode change places in charge and discharge, and anoxidation reaction and a reduction reaction occur on the correspondingsides; hence, an electrode with a high redox potential is called apositive electrode and an electrode with a low redox potential is calleda negative electrode. For this reason, in this specification, thepositive electrode is referred to as a “positive electrode” and thenegative electrode is referred to as a “negative electrode” in all thecases where charge is performed, discharge is performed, a reverse pulsecurrent is supplied, and a charging current is supplied. The use of theterms “anode” and “cathode” related to an oxidation reaction and areduction reaction might cause confusion because the anode and thecathode change places at the time of charging and discharging. Thus, theterms “anode” and “cathode” are not used in this specification. If theterm “anode” or “cathode” is used, it should be mentioned that the anodeor the cathode is which of the one at the time of charging or the one atthe time of discharging and corresponds to which of a positive electrodeor a negative electrode.

Two terminals in FIG. 19F are connected to a charger, and a secondarybattery 40 is charged. As the charge of the secondary battery 40proceeds, a potential difference between electrodes increases. Thepositive direction in FIG. 19F is the direction in which a current flowsfrom one terminal outside the secondary battery 40 to the positiveelectrode current collector 32, flows from the positive electrodecurrent collector 32 to the negative electrode current collector 34 inthe secondary battery 40, and flows from the negative electrode currentcollector 34 to the other terminal outside the secondary battery 40. Inother words, a current flows in the direction of a flow of a chargingcurrent.

Although an example of application to a lithium-ion secondary battery isdescribed in this embodiment, one embodiment of the present invention isnot limited to this example. Application to a variety of secondarybatteries such as a lead storage battery, a lithium-ion polymersecondary battery, a nickel-hydrogen storage battery, a nickel-cadmiumstorage battery, a nickel-iron storage battery, a nickel-zinc storagebattery, a silver oxide-zinc storage battery, a solid-state battery, andan air battery is also possible. Application to a variety of powerstorage devices such as a primary battery, a capacitor, and alithium-ion capacitor is also possible.

Embodiment 7

In this embodiment, an example of a structure that is partly differentfrom that of Embodiment 1 will be described with reference to FIGS. 25Aand 25B.

An example where the sizes and positions of three batteries aredifferent as illustrated in FIG. 25A will be described.

FIG. 25A is a plan view illustrating an example of the positionalrelation of the display portion 816 and the batteries.

A bendable portion 816 e of the display portion, which is shown by adotted line in FIG. 25A is located between a battery 812 and a battery817. A bendable portion 816 d of the display portion, which is shown bya dotted line in FIG. 25A, and a hinge 813 are located between thebattery 817 and a battery 853. A display region of the display portion816 has a size of approximately 9.2 inches.

In this embodiment, a gap between the batteries 817 and 853 is largerthan a gap between the batteries 812 and 817. The area of the battery817 is smaller than those of the other batteries. The batteries 817 and853 are fixed to the display portion 816 with an adhesive or the likeand also serve as supports of part of the display portion 816. Since thebatteries 812 and 817 are fixed to the display portion 816, anelectronic device can be smoothly bent along the bendable portion 816 eof the display portion when folded. Since the batteries 853 and 817 arefixed to the display portion 816, the electronic device can be smoothlybent along the bendable portion 816 d of the display portion whenfolded.

This embodiment is different from Embodiment 1 also in the structure ofthe display portion. In this embodiment, both ends of the displayportion do not have side rolled portions constantly bent. When theelectronic device is made small by being bent along the bendable portion816 d of the display portion, the periphery of the bendable portion 816d of the display portion becomes a side rolled portion.

To fix the electronic device when it is made small by being bent,magnets are provided at a plurality of portions of a housing.

FIG. 25B is a cross-sectional view of FIG. 25A and illustrates thepositional relation of components of the electronic device that isunfolded.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 8

In this embodiment, an example of a method for operating a touch panelthat can be used for a display panel included in the electronic deviceof one embodiment of the present invention will be described withreference to drawings.

[Example of Sensing Method of Sensor]

FIG. 26A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 26A illustrates a pulse voltage outputcircuit 601 and a current sensing circuit 602. Note that in FIG. 26A,six wirings X1 to X6 represent the electrodes 621 to which a pulsevoltage is applied, and six wirings Y1 to Y6 represent the electrodes622 that detect changes in current. FIG. 26A also illustrates acapacitor 603 that is formed where the electrodes 621 and 622 overlapwith each other. Note that functional replacement between the electrodes621 and 622 is possible.

The pulse voltage output circuit 601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 621 and 622 of the capacitor 603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 602 is a circuit for detecting changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 603. No change in currentvalue is detected in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value isdetected when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for sensing of current values.

FIG. 26B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 26A. In FIG. 26B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 26B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in accordance with the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change in accordance with changes inthe voltages of the wirings X1 to X6. The current value is decreased atthe point of approach or contact of a sensing target and accordingly thewaveform of the voltage value changes (portions indicated by arrows inFIG. 26B).

By detecting a change in mutual capacitance in this manner, the approachor contact of a sensing target can be sensed.

Although FIG. 26A is a passive touch sensor in which only the capacitor603 is provided at the intersection of wirings as a touch sensor, anactive touch sensor including a transistor and a capacitor may be used.FIG. 27 is a sensor circuit included in an active touch sensor.

The sensor circuit includes the capacitor 603 and transistors 611, 612,and 613. A signal G2 is input to a gate of the transistor 613. A voltageVRES is applied to one of a source and a drain of the transistor 613,and one electrode of the capacitor 603 and a gate of the transistor 611are electrically connected to the other of the source and the drain ofthe transistor 613. One of a source and a drain of the transistor 611 iselectrically connected to one of a source and a drain of the transistor612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 611. A signal G2 is input to a gate of thetransistor 612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 612. The voltage VSS isapplied to the other electrode of the capacitor 603.

Next, the operation of the sensor circuit will be described. First, apotential for turning on the transistor 613 is supplied as the signalG2, and a potential with respect to the voltage VRES is thus applied tothe node n connected to the gate of the transistor 611. Then, apotential for turning off the transistor 613 is applied as the signalG2, whereby the potential of the node n is maintained.

Then, mutual capacitance of the capacitor 603 changes owing to theapproach or contact of a sensing target such as a finger, andaccordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 612 issupplied as the signal G1. A current flowing through the transistor 611,that is, a current flowing through the wiring ML is changed inaccordance with the potential of the node n. By sensing this current,the approach or contact of a sensing target can be sensed.

It is preferred that the transistors 611, 612, and 613 each include anoxide semiconductor in a semiconductor layer where a channel is formed.In particular, by using an oxide semiconductor in a semiconductor layerwhere a channel of the transistor 613 is formed, the potential of thenode n can be held for a long time and the frequency of operation(refresh operation) of resupplying VRES to the node n can be reduced.

[Example of Driving Method for Display Device]

FIG. 28A is a block diagram illustrating an example of the structure ofa display device. FIG. 28A illustrates a gate driver circuit GD, asource driver circuit SD, and a pixel pix. In FIG. 28A, gate lines x_1to x_m (m is a natural number) electrically connected to the gate drivercircuit GD and source lines y_1 to y_n (n is a natural number)electrically connected to the source driver circuit SD are illustrated.Corresponding to these lines, the pixels pix are denoted by (1, 1) to(n, m).

FIG. 28B is a timing chart of signals supplied to the gate lines and thesource lines in the display device illustrated in FIG. 28A. The periodsin FIG. 28B show the case where data signals are rewritten every frameperiod and the case where data signals are not rewritten. Note thatperiods such as a retrace period are not taken into consideration inFIG. 28B.

In the case where data signals are rewritten every frame period, scansignals are sequentially input to the gate lines x_1 to x_m. In ahorizontal scanning period 1H, during which the scan signal is at Hlevel, data signals D are input to the source lines y_1 to y_n in thecolumns.

In the case where data signals are not rewritten every frame period, thesupply of scan signals to the gate lines x_1 to x_m is stopped. In thehorizontal scanning period the supply of data signals to the sourcelines y_1 to y_n in the columns is stopped.

A driving method in which data signals are not rewritten every frameperiod is effective particularly when an oxide semiconductor is used fora semiconductor layer where a channel of a transistor included in apixel is formed. A transistor including an oxide semiconductor can havemuch lower off-state current than a transistor including a semiconductorsuch as silicon. Thus, a data signal written in the previous period canbe held without rewriting data signals every frame period, and the graylevels of pixels can be held for 1 second or longer, preferably 5seconds or longer, for example.

[Examples of Driving Methods for Display Device and Touch Sensor]

FIGS. 29A to 29D show examples of the operations in successive frameperiods of the touch sensor described using FIGS. 26A and 26B and thedisplay device described using FIGS. 28A and 28B that are driven for 1sec (one second). In FIG. 29A, one frame period for the display deviceis 16.7 ms (frame frequency: 60 Hz), and one frame period for the touchsensor is 10.7 ms (frame frequency: 60 Hz).

In the touch panel of this embodiment, the display device and the touchsensor operate independently of each other, and the touch sensor canhave a touch sensing period concurrent with a display period. That iswhy one frame period for the display device and one frame period for thetouch sensor can both be 16.7 ms (frame frequency: 60 Hz) as shown inFIG. 29A. The frame period for the touch sensor may differ from that ofthe display device. For example, as shown in FIG. 29B, one frame periodfor the display device may be 8.3 ms (frame frequency: 120 Hz) and oneframe period for the touch sensor may be 16.7 ms (frame frequency: 60Hz). The frame frequency for the display device may be 33.3 ms (framefrequency: 30 Hz) (not shown).

The frame frequency for the display device may be changeable, i.e., theframe frequency in displaying moving images may be increased (e.g., 60Hz or more, or 120 Hz or more), whereas the frame frequency indisplaying still images may be decreased (e.g., 60 Hz or less, 30 Hz orless, or 1 Hz or less). With this structure, power consumption of thedisplay device can be reduced. The frame frequency for the touch sensormay be changeable so that the frame frequency in waiting is differ fromthe frame frequency in sensing a touch.

The touch panel of this embodiment holds data signals rewritten in theprevious period without rewriting data signals in the display device,and one frame period for the display device can thus be longer than 16.7ms. Thus, as shown in FIG. 29C, the operation can be switched so thatone frame period for the display device is 1 sec (frame frequency: 1 Hz)and one frame period for the touch sensor is 16.7 ms (frame frequency:60 Hz).

Furthermore, the touch panel of this embodiment can continue to operatethe touch sensor in the driving shown in FIG. 29C. Thus, data signals inthe display device can be rewritten at the timing at which the approachor contact of a sensing target is sensed by the touch sensor, as shownin FIG. 29D.

If rewriting of data signals in a display device is performed during asensing period of a touch sensor, noise caused by operating the displaydevice travels through the touch sensor and the sensitivity of the touchsensor might decrease. For this reason, rewriting of data signals in adisplay device and sensing in a touch sensor are preferably performed indifferent periods.

FIG. 30A shows an example in which rewriting of data signals in adisplay device and sensing in a touch sensor are performed alternately.FIG. 30B shows an example in which sensing in a touch sensor isperformed one time every two rewritings of data signals in a displaydevice. Note that sensing in a touch sensor may be performed once everythree or more rewritings.

With the use of an oxide semiconductor for a semiconductor layer where achannel of a transistor used in a pixel of a display device is formed,an off-state current can be significantly reduced and the frequency ofrewriting data signals can be sufficiently reduced. Specifically, asufficiently long break period can be set between rewritings of datasignals. The break period is 0.5 seconds or longer, 1 seconds or longer,or 5 seconds or longer, for example. The upper limit of the break perioddepends on the leakage current of a capacitor or a display elementconnected to a transistor; for example, 1 minutes or shorter, 10 minutesor shorter, 1 hour or shorter, or 1 day or shorter.

FIG. 30C shows an example in which rewriting of data signals in adisplay device is performed once every 5 seconds. A break period forstopping the operation of a display device is set in FIG. 30C betweenrewriting of data signals and next rewriting. In the break period, atouch sensor can be operated at a frame frequency of i Hz (i is morethan or equal to the frame frequency of a display device; here, 0.2 Hzor more). It is preferred that sensing in a touch sensor be performed ina break period and not be performed in a rewriting period of datasignals in a display device as shown in FIG. 30C, in which case thesensitivity of a touch sensor can be increased. When rewriting of datasignals and sensing are performed at the same time as shown in FIG. 30D,operation signals can be simplified.

In a break period during which rewriting of data signals in a displaydevice is not performed, only the supply of signals to a driver circuitmay be stopped, and in addition, the supply of a power supply potentialmay be stopped for further reducing power consumption.

The touch panel described in this embodiment includes a display deviceand a touch sensor between two flexible substrates. With this structure,the distance between the display device and the touch sensor can bereduced. A decrease in the sensitivity of the touch sensor caused bynoise generated by driving the display device can be suppressed byemploying the driving method in this embodiment, and both a reduction inthickness and high sensitivity of a touch panel are achieved.

Embodiment 9

In this embodiment, a structural example of a touch panel that can beused for a display panel included in the electronic device of oneembodiment of the present invention and an example of a method fordriving the touch panel will be described with reference to drawings.

[Configuration of Touch Panel]

FIG. 31 is a block diagram illustrating a configuration example of atouch panel that will be described below. As illustrated in FIG. 31, atouch panel 90 includes a display device 900, a control circuit 910, acounter circuit 920, and a touch sensor 950.

An image signal (Video), which is digital data, and a synchronizationsignal (SYNC) for controlling rewriting of a screen of the displaydevice 900 are input to the touch panel 90. Examples of synchronizationsignals include a horizontal synchronization signal (Hsync), a verticalsynchronization signal (Vsync), and a reference clock signal (CLK).

The display device 900 includes a display portion 901, a gate driver902, and a source driver 903. The display portion 901 includes aplurality of pixels PIX. The pixels PIX in the same row are connected tothe gate driver 902 through a common gate line L_X, and the pixels PIXin the sane column are connected to the source driver 903 through acommon source line L_Y.

A high-level voltage (VH), low-level voltage (VL), and a high powersupply voltage (VDD) and a low power supply voltage (VSS) which serve aspower supply voltages are applied to the display device 900. Thehigh-level voltage (hereinafter referred to as VH) is applied to eachpixel PIX in the display portion 901 through a common wiring L_H. Thelow-level voltage (hereinafter referred to as VL) is applied to eachpixel PIX in the display portion 901 through a wiring L_L.

The source driver 903 processes an input image signal to generate a datasignal, and outputs the data signal to the source line L_Y. The gatedriver 902 outputs, to the gate line L_X, a scan signal for selectingthe pixel PIX into which a data signal is to be written.

The pixel PIX includes a switching element whose electrical connectionto the source line is controlled by a scan signal. When the switchingelement is tamed on, a data signal is written into the pixel PIX throughthe source line L_Y.

The control circuit 910 controls the whole touch panel 90 and includes acircuit that generates control signals for circuits included in thetouch panel 90.

The control circuit 910 includes a control signal generation circuitthat generates control signals for the gate driver 902 and the sourcedriver 903 on the basis of the synchronization signal (SYNC). Examplesof control signals for the gate driver 902 include a start pulse (GSP)and a clock signal (GCLK). Examples of control signals for the sourcedriver 903 include a start pulse (SSP) and a clock signal (SCLK). Forexample, the control circuit 910 generates a plurality of clock signalswith the same cycle and shifted phases as the dock signals (GCLK andSCLK).

The control circuit 910 controls the output of an image signal (Video),which is input from the outside of the touch panel 90 to the sourcedriver 903.

In addition, a sensor signal (S_touch) is input to the control circuit910 from the touch sensor portion 950, and the control circuit 910corrects an image signal in accordance with the sensor signal. Thecorrection of the image signal depends on the sensor signal; imageprocessing corresponding to touch operation is performed.

The source driver 903 includes a digital/analog conversion circuit 904(hereinafter referred to as a D-A conversion circuit 904). The D-Aconversion circuit converts an image signal into an analog signal,thereby generating a data signal.

Note that in the case where an image signal input to the touch panel 90is an analog signal, the image signal is converted into a digital signalin the control circuit 910 and output to the display device 900.

An image signal is image data for each frame. The control circuit 910has a function of performing image processing on the image data andcontrolling output of the image signal to the source driver 903 on thebasis of data obtained by the processing. For that function, the controlcircuit 910 includes a motion sensing portion 911 that performs imageprocessing on the image data to sense motion in the image data for eachframe. In the case where a sensor signal is input, the image signalbased on the image data is corrected in response to the sensor signal.

When the motion sensing portion 911 determines that there is motion, thecontrol circuit 910 continues to output image signals to the sourcedriver 903. The control circuit 910 stops the output of image signals tothe source driver 903 when the motion sensing portion 911 determinesthat there is no motion, and restarts the output of image signals whenthe motion sensing portion 911 determines that there is motion.

The control circuit 910 can control display in the display portion 901by switching between a first mode for displaying images with motion(moving image display) and a second mode for displaying images withoutmotion (still image display) based on determination by the motionsensing portion 911. In the first mode, when the frequency of thevertical synchronization signal (Vsync) is 60 Hz, for example, the framefrequency is set to 60 Hz or higher, in the second mode, when thefrequency of the vertical synchronization signal (Vsync) is 60 Hz, forexample, the frame frequency is set to lower than 60 Hz.

The frame frequency in the second mode is preferably set in advance inaccordance with a voltage holding property of a pixel. For example, whenthe motion sensing portion 911 determines that there is no motion for acertain period of time and the control circuit 910 stops the output ofimage signals to the source driver 903, a voltage corresponding to thegray level of an image signal that is written in the pixel PIX islowered. Therefore, it is preferable to write in a voltage correspondingto the gray level of an image signal for the same image in accordancewith the frame frequency (such operation is also called refreshoperation). The timing of the refresh operation (also referred to as arefresh rate) is set such that the refresh operation is performed everycertain period of time. The timing is based on, for example, a signalobtained by counting the H level of the vertical synchronization signal(Vsync) in the counter circuit 920.

In the case where the refresh rate is set to once every second, when thefrequency of the vertical synchronization signal (Vsync) is 60 Hz, forexample, refresh operation is performed in response to a count signal(Count) that is output after the counter circuit 920 counts the H levelof the vertical synchronization signal (Vsync) up to 60. In the casewhere the refresh rate is set to once every five seconds, when thefrequency of the vertical synchronization signal (Vsync) is 60 Hz, forexample, refresh operation is performed in response to a count signal(Count) that is output after the counter circuit 920 counts the H levelof the vertical synchronization signal (Vsync) up to 300. Furthermore,the following operation is possible: when a sensor signal is input fromthe touch sensor portion 950, the counter circuit 920 forcibly switchesthe control circuit 910 from the second mode to the first mode inresponse to the sensor signal.

Note that there is no particular limitation on the image processing forsensing motion that is performed in the motion sensing portion 911. Anexample of a method for sensing motion is to obtain difference data fromimage data for two consecutive frames. It can be determined whetherthere is motion or not from the obtained difference data. Anotherexample of the method is to sense a motion vector.

The operation and structure described in the above embodiment can beused for the touch sensor 950.

The display device and the touch sensor 950 of this embodiment operateindependently of each other; thus, the touch sensor portion 950 can havea touch sensing period concurrent with a display period. Even in thestructure in which the control circuit 910 switches between the firstmode and the second mode, the operation of the touch sensor can thus becontrolled independently of those modes. By synchronizing the operationof the display device 900 with the operation of the touch sensor 950 andperforming rewriting of data signal in the display device 900 andsensing in the touch sensor 950 in different periods, the sensitivity ofsensing can be increased.

[Configuration Example of Pixel]

FIG. 32A is a circuit diagram illustrating a configuration example ofthe pixel PIX. The pixel PLX includes a transistor TR1, a transistorTR2, a light-emitting element EL, and a capacitor Cap.

The transistor TR1 is a switching element that controls electricalconnection between the source line L_Y and a gate of the transistor TR2.The transistor TR1 is turned on or off by a scan signal input to itsgate. The transistor TR2 is a switching element that controls a currentsupplied to the light-emitting element EL.

Note that an oxide semiconductor is preferably used for a semiconductorlayer where a channel is formed in the transistors TR1 and TR2.

The light-emitting element EL includes an EL layer containing alight-emitting organic compound between two electrodes. The emissionluminance, of the light-emitting element depends on a current flowingthrough the electrodes. A low-level voltage is applied from the wiringL_L to one electrode of the light-emitting element, and a high-levelvoltage is applied from the wiring L_H to the other electrode via thetransistor TR2.

The capacitor Cap retains the potential of the gate of the transistorTR2.

FIG. 32B is an example of the pixel PIX including a liquid crystalelement. The pixel PIX includes a transistor TR, a liquid crystalelement LC, and a capacitor Cap.

The transistor TR is a switching element that controls electricalconnection between the liquid crystal element LC and the source lineL_Y. The transistor TR is turned on or off by a scan signal input to itsgate.

Note that an oxide semiconductor is preferably used for a semiconductorlayer where a channel is formed in the transistor TR.

The liquid crystal element LC includes two electrodes and a liquidcrystal. The alignment of the liquid crystal is changed by the action ofan electric field between the two electrodes. One of the two electrodesof the liquid crystal element LC, which is connected to the source lineL_Y through the transistor TR, is a pixel electrode, and the other, towhich Vcom is applied, is connected to a common line L_com.

The capacitor Cap is connected in parallel with the liquid crystalelement LC. Here, one electrode of the capacitor is an electrodeconnected to a source or a drain of the transistor TR, and the otherelectrode of the capacitor is connected to the capacitor line L_cap towhich a capacitor line voltage is applied.

Note that although the light-emitting element LC or the light-emittingelement EL is used as a display element here, one embodiment of thepresent invention is not limited thereto.

For example, in this specification and the like, a display element, adisplay device, which is a device including a display element, alight-emitting element, and a light-emitting device, which is a deviceincluding a light-emitting element, can employ a variety of modes or caninclude a variety of elements. Examples of a display element, a displaydevice, a light-emitting element, or a light-emitting device include atleast one of an electroluminescence (EL) element (e.g., an EL elementincluding organic and inorganic materials, an organic EL element, and aninorganic EL element), an LED (e.g., a white LED, a red LED, a greenLED, and a blue LED), a transistor (a transistor that emits lightdepending on current), an electron emitter, a liquid crystal element,electronic ink, an electrophoretic element, a grating light valve (GLV),a plasma display panel (PDP), a display element using micro electromechanical system (MEMS), a digital micromirror device (DMD), a digitalmicro shutter (DMS), MIRASOL (registered trademark), an interferometricmodulation (IMOD) element, a MEMS shutter display element, anoptical-interference-type MEMS display element, an electrowettingelement, a piezoelectric ceramic display, and a display element using acarbon nanotube. Other than the above, a display medium whose contrast,luminance, reflectance, transmittance, or the like is changed byelectrical or magnetic action may be included. Note that examples ofdisplay devices using EL elements include an EL display. Examples ofdisplay devices including electron emitters include a field emissiondisplay (FED) and an SED-type flat panel display (SED:surface-conduction electron-emitter display). Examples of displaydevices using liquid crystal elements include a liquid crystal display(e.g., a transmissive liquid crystal display, a transflective liquidcrystal display, a reflective liquid crystal display, a direct-viewliquid crystal display, and a projection liquid crystal display). Anexample of a display device including electronic ink or electrophoreticelements is electronic paper. In the case of a transflective liquidcrystal display or a reflective liquid crystal display, some or all ofpixel electrodes function as reflective electrodes. For example, some orall of pixel electrodes are formed to contain aluminum, silver, or thelike. In such a case, a storage circuit such as an SRAM can be providedunder the reflective electrodes, leading to lower power consumption.

For example, in this specification and the like, an active matrix methodin which an active element is included in a pixel or a passive matrixmethod in which an active element is not included in a pixel can beused.

In an active matrix method, as an active element (a non-linear element),not only a transistor but also various active elements (non-linearelements) such as a MIM (metal insulator metal), and a TFD (thin filmdiode) can be used. Since such an element has few numbers ofmanufacturing steps, the manufacturing cost can be reduced or the yieldcan be improved. Alternatively, since the size of the element is small,the aperture ratio can be improved, so that power consumption can bereduced or higher luminance can be achieved.

Note that as a method other than an active matrix method, a passivematrix method in which an active element (a non-linear element) is notused can also be used. Since an active element (a non-linear element) isnot used, the number of manufacturing steps is small, so that themanufacturing cost can be reduced or the yield can be improved.Alternatively, since an active element (a non-linear element) is notused, the aperture ratio can be improved, so that power consumption canbe reduced or higher luminance can be achieved, for example.

[Example of Driving Method for Touch Panel]

The operation of the touch panel 90, which performs display in the firstmode for moving image display and in the second mode for still imagedisplay, will be described below with reference to a timing chart inFIG. 33. FIG. 33 shows the signal waveforms of the verticalsynchronization signal (Vsync) and a data signal (Vdata) that is outputto the source line L_Y from the source driver 903.

FIG. 33 is a timing chart of the touch panel 90. In FIG. 33, forexample, moving image display, still image display, and moving imagedisplay are performed in that order. Here, there is motion in image datafor the first to k-th frames. There is no motion in image data for the(k+1)-th to (k+3)-th frames. There is motion in image data for the(k+4)-th frame and frames after the (k+4)-th frame. Note that k is aninteger of 2 or more.

In the first moving image display period, the motion sensing portion 911determines that there is motion in image data for each frame, and thetouch panel 90 operates in the first mode. The control circuit 910outputs image signals (Video) to the source driver 903 at a framefrequency f₁ that is higher than or equal to the frequency of thevertical synchronization signal. The source driver 903 continuouslyoutputs data signals (Vdata) to the source line L_Y. Note that thelength of one frame period in the moving image display period isrepresented by 1/f₁ (seconds).

Next, in the still image display period, the motion sensing portion 911performs image processing for sensing motion and determines that thereis no motion in image data for the (k+1)-th frame, and the touch panel90 operates in the second mode. The control circuit 910 outputs imagesignals (Video) to the source driver 903 at a frame frequency f₂ that islower than the frequency of the vertical synchronization signal. Thesource driver 903 intermittently outputs data signals (Vdata) to thesource line L_Y. Note that the length of one frame period in the stillimage display period is represented by 1/f₂ (seconds).

Since the source driver 903 intermittently outputs data signals (Vdata),the supply of control signals (e.g., a start pulse signal and a clocksignal) to the gate driver 902 and the source driver 903 can also beperformed intermittently; thus, the operations of the gate driver 902and the source driver 903 can be stopped at regular intervals.

The intermittent output of data signals (Vdata) to the source line, L_Yin the second mode will be specifically described. For example, as shownin FIG. 33, in the (k+1)-th frame, the control circuit 910 outputscontrol signals to the gate driver 902 and the source driver 903 andoutputs image signals (Video) to the source driver 903 at the framefrequency f₂. The source driver 903 outputs the data signal (Vdata)written in the previous period, that is, the data signal (Vdata) outputto the source line L_Y in the k-th frame, to the source line L_Y. Inthis manner, in the still image display period, the data signal (Vdata)written in the previous period is repeatedly written to the source lineL_Y every 1/f₂ seconds. Thus, a voltage corresponding to the gray levelof an image signal for the same image can be written (i.e., refreshoperation can be performed). Refresh operations performed at regularintervals can reduce flickers due to the shift of gray levels caused bya voltage drop and can improve the display quality of the touch panel.

The control circuit 910 operates in the second mode until the motionsensing portion 911 determines that there is motion in image data oruntil a sensor signal is input.

Then, when the motion sensing portion 911 determines that there ismotion in image data for the (k+4)-th frame and frames after the(k+4)-th frame, the touch panel 90 operates in the first mode again. Thecontrol circuit 910 outputs image signals (Video) to the source driver903 at the frame frequency f₁ that is higher than or equal to thefrequency of the vertical synchronization signal. The source driver 903continuously outputs data signals (Vdata) to the source line L_Y.

The touch panel described in this embodiment includes a display deviceand a touch sensor between two flexible substrates, for example. Withthis structure, the display device and the touch sensor can be extremelyclose to each other. A decrease in sensitivity of the touch sensorcaused by noise generated by driving the display device can besuppressed by employing the driving method in this embodiment, and bothreduction in thickness and high sensitivity of a touch panel areachieved.

Note that what is described (or part thereof) in one embodiment can beapplied to, combined with, or replaced with different contents in theembodiment and/or what is described (or part thereof) in anotherembodiment or other embodiments.

Note that in each embodiment, what is described in the embodiment iscontents described with reference to a variety of diagrams or contentsdescribed with text described in this specification.

Note that by combining a diagram (or may be part of the diagram)illustrated in one embodiment with another part of the diagram, adifferent diagram (or may be part of the different diagram) illustratedin the embodiment, and/or a diagram (or may be part of the diagram)illustrated in another embodiment or other embodiments, much morediagrams can be formed.

Note that contents that are not specified in any drawing or text in thespecification can be excluded from one embodiment of the invention.Alternatively, when the range of a value that is defined by the maximumand minimum values is described, part of the range is appropriatelynarrowed or part of the range is removed, whereby one embodiment of theinvention excluding part of the range can be constituted. In thismanner, it is possible to specify the technical scope of one embodimentof the present invention so that a conventional technology is excluded,for example.

As a specific example, a diagram of a circuit including first to fifthtransistors is illustrated. In that case, it can be specified that thecircuit does not include a sixth transistor in the invention. It can bespecified that the circuit does not include a capacitor in theinvention. It can be specified that the circuit does not include a sixthtransistor with a particular connection structure in the invention. Itcan be specified that the circuit does not include a capacitor with aparticular connection structure in the invention. For example, it can bespecified that a sixth transistor whose gate is connected to a gate ofthe third transistor is not included in the invention. For example, itcan be specified that a capacitor whose first electrode is connected tothe gate of the third transistor is not included in the invention.

As another specific example, the description of a value, “a voltage ispreferably higher than or equal to 3 V and lower than or equal to 10 V”is given. In that case, for example, it can be specified that the casewhere the voltage is higher than or equal to −2 V and lower than orequal to 1 V is excluded from one embodiment of the invention. Forexample, it can be specified that the case where the voltage is higherthan or equal to 13 V is excluded from one embodiment of the invention.Note that, for example, it can be specified that the voltage is higherthan or equal to 5 V and lower than or equal to 8 V in the invention.For example, it can be specified that the voltage is approximately 9 Vin the invention. For example, it can be specified that the voltage ishigher than or equal to 3 V and lower than or equal to 10 V but is not 9V in the invention. Note that even when the description “a value ispreferably in a certain range” or “a value preferably satisfies acertain condition” is given, the value is not limited to thedescription. In other words, a description of a value that includes aterm “preferable”, “preferably”, or the like does not necessarily limitthe value.

As another specific example, the description “a voltage is preferred tobe 10 V” is given. In that case, for example, it can be specified thatthe case where the voltage is higher than or equal to −2 V and lowerthan or equal to 1 V is excluded from one embodiment of the invention.For example, it can be specified that the case where the voltage ishigher than or equal to 13 V is excluded from one embodiment of theinvention.

As another specific example, the description “a film is an insulatingfilm” is given to describe a property of a material. In that case, forexample, it can be specified that the case where the insulating film isan organic insulating film is excluded from one embodiment of theinvention. For example, it can be specified that the case where theinsulating film is an inorganic insulating film is excluded from oneembodiment of the invention. For example, it can be specified that thecase where the insulating film is a conductive film is excluded from oneembodiment of the invention. For example, it can be specified that thecase where the insulating film is a semiconductor film is excluded fromone embodiment of the invention.

As another specific example, the description of a stacked structure, “afilm is provided between an A film and a B film” is given. In that case,the example, it can be specified that the case where the film is alayered film of four or more layers is excluded from the invention. Forexample, it can be specified that the case where a conductive film isprovided between the A film and the film is excluded from the invention.

Note that various people can implement one embodiment of the inventiondescribed in this specification and the like. However, different peoplemay be involved in the implementation of the embodiment of theinvention. For example, in the case of a transmission/reception system,the following case is possible: Company A manufactures and sellstransmitting devices, and Company B manufactures and sells receivingdevices. As another example, in the case of a light-emitting deviceincluding a transistor and a light-emitting element, the following caseis possible: Company A manufactures and sells semiconductor devicesincluding transistors, and Company B purchases the semiconductordevices, provides light-emitting elements for the semiconductor devices,and completes light-emitting devices.

In such a case, one embodiment of the invention can be constituted sothat a patent infringement can be claimed against each of Company A andCompany B. In other words, one embodiment of the invention can beconstituted so that only Company A implements the embodiment, andanother embodiment of the invention can be constituted so that onlyCompany B implements the embodiment. One embodiment of the inventionwith which a patent infringement suit can be filed against Company A orCompany B is clear and can be regarded as being disclosed in thisspecification or the like. For example, in the case of atransmission/reception system, even when this specification or the likedoes not include a description of the case where a transmitting deviceis used alone or the case where a receiving device is used alone, oneembodiment of the invention can be constituted by only the transmittingdevice and another embodiment of the invention can be constituted byonly the receiving device. Those embodiments of the invention are clearand can be regarded as being disclosed in this specification or thelike. Another example is as follows: in the case of a light-emittingdevice including a transistor and a light-emitting element, even whenthis specification or the like does not include a description of thecase where a semiconductor device including the transistor is used aloneor the case where a light-emitting device including the light-emittingelement is used alone, one embodiment of the invention can beconstituted by only the semiconductor device including the transistorand another embodiment of the invention can be constituted by only thelight-emitting device including the light-emitting element. Thoseembodiments of the invention are clear and can be regarded as beingdisclosed in this specification or the like.

Note that in this specification and the like, it may be possible forthose skilled in the art to constitute one embodiment of the inventioneven when portions to which all the terminals of an active element(e.g., a transistor or a diode), a passive element (e.g., a capacitor ora resistor), and the like are connected are not specified. In otherwords, one embodiment of the invention is clear even when connectionportions are not specified. Further, in the case where a connectionportion is disclosed in this specification and the like, it can bedetermined that one embodiment of the invention in which a connectionportion is not specified is disclosed in this specification and thelike, in some cases. In particular, in the case where the number ofportions to which the terminal is connected may be more than one, it isnot necessary to specify the portions to which the terminal isconnected. Therefore, it may be possible to constitute one embodiment ofthe invention by specifying only portions to which some of terminals ofan active element (e.g., a transistor or a diode), a passive element(e.g., a capacitor or a resistor), and the like are connected.

Note that in this specification and the like, it may be possible forthose skilled in the art to specify the invention when at least theconnection portion of a circuit is specified. Alternatively, it may bepossible for those skilled in the art to specify the invention when atleast a function of a circuit is specified. In other words, when afunction of a circuit is specified, one embodiment of the presentinvention is clear. Moreover, it can be determined that one embodimentof the present invention whose function is specified is disclosed inthis specification and the like. Therefore, when a connection portion ofa circuit is specified, the circuit is disclosed as one embodiment ofthe invention even when a function is not specified, and one embodimentof the invention can be constituted. Alternatively, when a function of acircuit is specified, the circuit is disclosed as one embodiment of theinvention even when a connection portion is not specified, and oneembodiment of the invention can be constituted.

Note that in this specification and the like, part of a diagram or textdescribed in one embodiment can be taken out to constitute oneembodiment of the invention. Thus, in the case where a diagram or textrelated to a certain portion is described, the contents taken out frompart of the diagram or the text are also disclosed as one embodiment ofthe invention, and one embodiment of the invention can be constituted.The embodiment of the present invention is clear. Therefore, forexample, in a diagram or text in which one or more active elements(e.g., transistors or diodes), wirings, passive elements (e.g.,capacitors or resistors), conductive layers, insulating layers,semiconductor layers, organic materials, inorganic materials,components, devices, operating methods, manufacturing methods, or thelike are described, part of the diagram or the text is taken out, andone embodiment of the invention can be constituted. For example, from acircuit diagram in which N circuit elements (e.g., transistors orcapacitors; N is an integer) are provided, it is possible to take out Mcircuit elements (e.g., transistors or capacitors; M is an integer,where M<N) and constitute one embodiment of the invention. For anotherexample, it is possible to take out layers (M is an integer, where M<N)from a cross-sectional view in which N layers (N is an integer) areprovided and constitute one embodiment of the invention. For anotherexample, it is possible to take out M elements (M is an integer, whereM<N) from a flow chart in which N elements (N is an integer) areprovided and constitute one embodiment of the invention. For anotherexample, it is possible to take out some given elements from a sentence“A includes B, C, D, E, or F” and constitute one embodiment of theinvention, for example, “A includes B and E”, “A includes E and F”, “Aincludes C, E, and F”, or “A includes B, C, D, and E”.

Note that in the case where at least one specific example is describedin a diagram or text described in one embodiment in this specificationand the like, it will be readily appreciated by those skilled in the artthat a broader concept of the specific example can be derived.Therefore, in the diagram or the text described in one embodiment, inthe case where at least one specific example is described, a broaderconcept of the specific example is disclosed as one embodiment of theinvention, and one embodiment of the invention can be constituted. Theembodiment of the present invention is clear.

Note that in this specification and the like, what is illustrated in atleast a diagram (which may be part of the diagram) is disclosed as oneembodiment of the invention, and one embodiment of the invention can beconstituted. Therefore, when certain contents are described in adiagram, the contents are disclosed as one embodiment of the inventioneven when the contents are not described with text, and one embodimentof the invention can be constituted. In a similar manner, part of adiagram, which is taken out from the diagram, is disclosed as oneembodiment of the invention, and one embodiment of the invention can beconstituted. The embodiment of the present invention is clear.

EXPLANATION OF REFERENCE

1: FPC, 2: FPC, 4: FPC, 5: FPC, 10: housing, 11: housing, 12: housing,13: hinge, 14: window portion, 16: base, 16 a: barrier film, 16 b: base,16 c: resin layer, 17: protective base, 17 p: protective layer, 19:sensing circuit, 20: sensor, 20U: sensing unit, 21: electrode, 22:electrode, 23: insulating layer, 31: film, 32: positive electrodecurrent collector, 33: separator, 34: negative electrode currentcollector, 35: sealing layer, 36: lead electrode, 37: negative electrodeactive material layer, 38: positive electrode active material layer, 39:negative electrode active material layer, 40: secondary battery, 41:adhesive layer, 42: electrolytic solution, 90: touch panel, 100: inputdevice, 110: device, 111: CPU, 112: battery, 113: regulator, 114:wireless receiving portion, 115: control module, 116: display portion,116 a: side rolled portion, 116 b: side roiled portion, 116 c: siderolled portion, 117: battery, 118: regulator, 119; display drivercircuit, 120: wireless receiving portion, 121: display module, 125:system portion, 127: power management circuit, 128: wirelesstransmitting portion, 129: wireless transmitting portion, 140: circuitboard, 141: lead electrode, 142: Part of driver circuit, 143: flexiblefilm, 144: flexible film, 150: wireless transmitting portion, 152: touchsensor, 153: battery, 154: regulator, 156: touch input portion, 159:sensor driver circuit, 160: fold position sensor, 201: formationsubstrate, 203: separation layer, 205: layer to be separated, 207:bonding layer, 211: bonding layer, 221: formation substrate, 223:separation layer, 225: layer to be separated, 226: insulating layer,231: substrate, 233: bonding layer, 401: electrode, 402: EL layer, 403:electrode, 404: bonding layer, 404 a: bonding layer, 404 b: bondinglayer, 405: insulating layer, 407: bonding layer, 420: flexiblesubstrate, 422: adhesive layer, 424: insulating layer, 426: adhesivelayer, 428: flexible substrate, 431: light-blocking layer, 432: coloringlayer, 435: conductive layer, 441: conductive layer, 442: conductivelayer, 443: insulating layer, 444: flexible substrate, 445: FPC, 450:organic EL element, 453: overcoat, 454: transistor, 455: transistor,457: conductive layer, 463: insulating layer, 465: insulating layer,467: insulating, layer, 491: light-emitting portion, 493: driver circuitportion, 495: FPC, 496: spacer, 497: connector, 500: input/outputdevice, 501: display portion, 502: pixel, 502B: sub-pixel, 502G:sub-pixel, 502R: sub-pixel, 502 t: transistor, 503 c: capacitor, 503 g:scan line driver circuit, 503 t: transistor, 510: base, 510 a: barrierfilm, 510 b: base, 510 c: resin layer, 511: wiring, 519: terminal, 521:insulating film, 528: partition wall, 550R: light-emitting element, 560:sealant, 567 p: anti-reflective layer, 580R: light-emitting module, 601:pulse voltage output circuit, 602: current sensing circuit, 603:capacitor, 611: transistor, 612: transistor, 613: transistor, 621:electrode, 622: electrode, 717: battery, 718: regulator, 753: battery,754: regulator, 812: battery, 813: hinge, 816: display portion, 817:battery, 853: battery, 900: display device, 901: display portion, 902:gate driver, 903: source driver, 904: digital/analog conversion circuit,910: control circuit, 911: motion sensing portion, 920: counter circuit,950: touch sensor, 1700: curved surface, 1701: plane, 1702: curve, 1703:radius of curvature, 1704: center of curvature, 1800: center ofcurvature, 1801: film, 1802: radius of curvature, 1803: film, 1804:radius of curvature, and 1805: layer

This application is based on Japanese Patent Application serial no.2014-039913 filed with the Japan Patent Office on Feb. 28, 2014 andJapanese Patent Application serial no. 2014-045237 filed with the JapanPatent Office on Mar. 7, 2014, the entire contents of which are herebyincorporated by reference.

What is claimed is:
 1. An electronic device comprising: a displayportion including a display surface and a back surface; a touch inputportion over the display surface; and a first battery, a second battery,and a system portion over the back surface; wherein a first bendableportion is provided in the display portion between the first battery andthe second battery, wherein a second bendable portion is provided in thedisplay portion between the second battery and the system portion, andwherein the first battery is electrically connected to the displayportion and the touch input portion, and wherein the second battery iselectrically connected to the system portion.
 2. The electronic deviceaccording to claim 1, wherein the touch input portion includes atransistor including an oxide semiconductor layer.
 3. The electronicdevice according to claim 1, further comprising a power managementcircuit, wherein the power management circuit has a function ofwirelessly transmitting power of the first battery to the secondbattery.
 4. The electronic device according to claim 1, wherein thefirst battery overlaps with the second battery in a state where thedisplay portion is folded.
 5. An electronic device comprising: a displayportion including a display surface and a back surface; a touch inputportion over the display surface; and a first battery, a second battery,a third battery, and a system portion over the back surface, the thirdbattery overlapping with the system portion; wherein a first bendableportion is provided in the display portion between the first battery andthe second battery, wherein a second bendable portion is provided in thedisplay portion between the second battery and the third battery, andwherein the first battery is electrically connected to the touch inputportion, wherein the second battery is electrically connected to thedisplay portion, and wherein the third battery is electrically connectedto the system portion.
 6. The electronic device according to claim 5,wherein the touch input portion includes a transistor including an oxidesemiconductor layer.
 7. The electronic device according to claim 5,further comprising a power management circuit, wherein the powermanagement circuit has a function of wirelessly supplying power amongthe first battery, the second battery, and the second battery.
 8. Theelectronic device according to claim 5, wherein the first batteryoverlaps with the second battery and the third battery in a state wherethe display portion is folded.
 9. An electronic device comprising: adisplay portion including a display surface and a back surface; a touchinput portion over the display surface; and a first battery, a secondbattery, and a system portion over the back surface, the second batteryoverlapping with the system portion; wherein a bendable portion isprovided in the display portion between the first battery and the secondbattery, wherein the first battery is electrically connected to thedisplay portion and the touch input portion, and wherein the secondbattery is electrically connected to the system portion.
 10. Theelectronic device according to claim 9, wherein the touch input portionincludes a transistor including an oxide semiconductor layer.
 11. Theelectronic device according to claim 9, further comprising a powermanagement circuit, wherein the power management circuit has a functionof wirelessly transmitting power of the first battery to the secondbattery.
 12. The electronic device according to claim 9, wherein thefirst battery overlaps with the second battery in a state where thedisplay portion is folded.